Method for producing wax from thermal decomposition of plastic

Abstract

The present invention relates to producing hydrocarbon products from a polymer feed. In particular, the present invention relates to producing wax from a polymer feed by pyrolysis and hydrogenation of the fluid product stream from the pyrolysis.

Description

Technical Field

[0001] The present invention relates to producing hydrocarbon products from a polymer feed. In particular, the present invention relates to producing wax from a polymer feed by pyrolysis and hydrogenation of the fluid product stream from pyrolysis.

Background Art

[0002] Plastics are one of the most commonly used materials due to their low cost and versatility. They are often produced for single-use purposes and account for approximately 10% of the commercial and household waste generated.

[0003] Plastic waste is not biodegradable and can remain in the environment for centuries if not disposed of using appropriate methods, posing unique problems. Currently widely used methods for handling plastic waste include landfilling, incineration, and recycling. Since the current capacity of recycling and incineration facilities is small compared to landfilling capacity, most plastic waste ends up being landfilled. This is not consistent with the current efforts towards increased recycling and the use of environmental processes.

[0004] In incineration, some of the energy stored in the plastic returns in the form of thermal energy that can be used to generate steam, which can in turn be used to generate electricity. One of the biggest drawbacks of incineration is the production of carcinogenic furans and dioxin emissions. Another drawback of incineration is the form of the product. Incineration generates heat, but this energy is lost when transported over long distances and can only be utilized in the immediate vicinity.

[0005] Plastic waste can be reused to produce new plastic products and can also be recycled into plastic materials that can be used to produce new plastic products. However, the reuse of plastics requires time and labor-intensive collection and separation, which makes the method less technically and economically feasible. The separation of plastics is difficult, cross-contamination is almost always inevitable, and recycled products that can only be used for low-grade applications are produced. Thorough cleaning is also required before the reuse process, generating additional waste.

[0006] The thermal decomposition of plastics is one of the most promising plastic disposal methods for recovering energy from waste plastics in gaseous, liquid, and solid forms while minimizing the impurities emitted. Thermal decomposition is the thermal breakdown of materials at high temperatures in the absence of oxygen. Therefore, neither combustion nor oxidation occurs. In the thermal decomposition of plastics, plastic waste is heated to a high temperature and the waste is decomposed into combustible gaseous, liquid, and solid products.

[0007] Thermal decomposition is currently considered the third reuse method as an excellent way to recover energy from plastic waste or to produce useful products such as energy sources and chemical feedstocks. Compared with incineration, thermal decomposition produces fewer toxic gases and has a higher energy recovery efficiency. The thermal decomposition products are much more versatile and easier to transport compared to the thermal energy produced during incineration.

[0008] Thermal decomposition is also less affected by plastic cross-contamination than plastic reuse and therefore does not require thorough separation treatment, making it more feasible than plastic reuse. Thermal decomposition is considered a promising green technology because even its gaseous by-products have a significant calorific value and can be reused at the thermal decomposition stage to reduce the energy required for the thermal decomposition plant.

[0009] The thermal decomposition of plastics has typically focused on the conditions applied during thermal decomposition in order to maximize the yield of a particular desired product, such as wax. For example, wax production from plastics typically targets vacuum pyrolysis, which can increase the proportion of wax (e.g., C 20+ hydrocarbons) under reduced pressure, e.g., less than 0.5 atm. However, while there are numerous factors that affect product yield and product composition (e.g., including operating temperature, heat consumption rate, residence time), the process is typically designed to shift the distribution towards lighter products, increasing losses to non-condensable gases or sacrificing lighter fractions to produce waxes with long carbon chains. However, this can have an adverse effect on the production of certain hydrocarbons during the distribution, such as light waxes.

Summary of the Invention

Problems to be Solved by the Invention

[0010] Therefore, it is desirable to develop a new method designed to more efficiently obtain useful product streams, such as light waxes, from the thermal decomposition of plastics.

Means for Solving the Problems

[0011] Surprisingly, it has been found that by performing controlled pyrolysis in a rotary kiln reactor and hydrogenating the pyrolysis products obtained from the reactor prior to further processing, the distribution of hydrocarbon products from the pyrolysis process can be improved. In particular, the method has been found to yield light waxes in advantageous yields that can be efficiently separated from the liquid products. In typical wax production methods by pyrolysis, the process is designed to maximize the yield of overall C 20+ products and shift the distribution towards an increase in the proportion of heavy waxes. However, surprisingly, by using this method, where the distribution of hydrocarbon products shifts away from an increase in overall wax production, compared to other vacuum pyrolysis methods, C 20It has been found that the production of less liquid product can be increased and an advantageous wax product distribution can be achieved with respect to light waxes. For example, counterintuitively, by producing less wax in the process, an improvement in the production of valuable light waxes (e.g., waxes having a melting point of less than 100 °C, preferably less than 85 °C) can be achieved.

[0012] Accordingly, an aspect of the present invention is a method for producing a wax having a melting point of less than 100 °C from a polymer feed, comprising: (i) providing a polymer feed comprising at least 80 wt% of a polyolefin polymer; (ii) melting the polymer feed to provide a molten polymer feed; (iii) feeding the molten polymer feed to a rotary kiln reactor comprising a plurality of sequential heating zones, each zone of the rotary kiln being operated at a temperature of 300 °C to 800 °C to pyrolyze the molten polymer feed to produce a fluid product stream and a solid char product; (iv) separating the solid char product from the fluid product stream; (v) C 5+ feeding the liquid fraction of the fluid product stream containing hydrocarbons to a hydrogenation reactor to hydrogenate the liquid fraction to produce a hydrogenated hydrocarbon product stream; (vi) fractionating the hydrogenated hydrocarbon product stream to produce a C 20+ wax fraction having a melting point of less than 100 °C; (vii) fractionating the C 20+ wax fraction to produce two or more separate wax fractions, each having a melting point of less than 100 °C A method is provided.

[0013] By pyrolyzing a plastic polymer in a temperature-controlled rotary kiln and hydrogenating the effluent from the kiln, the process has been found to provide an advantageous hydrocarbon product distribution for producing certain light waxes. In particular, by using this process, the yield of light waxes having a melting point below 100 °C is increased, such that it has been found that several different wax fractions, all having a melting point below 100 °C, can be separated to be provided. In particular, the wax fractions produced can be easily separated from the lighter hydrocarbon liquid fraction (C 20 less than), and the wax fractions can be separated into various light wax fractions without the need for removal of heavy wax fractions from the light waxes. In this way, an increase in the amount of thermal energy required to separate heavy wax fractions from light waxes (due to the high boiling points of the wax components) can be avoided, providing a more energy-efficient production of light waxes.

[0014] A further aspect of the invention is an apparatus for producing a wax having a melting point below 100 °C from a polymer feed, (i) means for melting a polymer feed comprising at least 80 wt% polyolefin polymer to provide a molten polymer feed, (ii) a rotary kiln reactor configured to receive the molten polymer feed from part (i), configured to provide a plurality of sequential heating zones, each zone of the rotary kiln being operated at a temperature of 300 °C to 800 °C to pyrolyze the molten polymer feed to produce a fluid product stream and a solid char product, a rotary kiln reactor, (iii) means for separating the solid char product from the fluid product stream, and (iv) a hydrogenation reactor configured to receive the liquid fraction of the fluid product stream containing C 5+ hydrocarbons and hydrogenating the liquid fraction to produce a hydrogenated hydrocarbon product stream, (v) fractionating the hydrogenated hydrocarbon product stream to produce C having a melting point below 100 °C 20+Means for producing a wax fraction (vi) C from (v) 20+ Means for fractionating the wax fraction to produce two or more separate wax fractions, each having a melting point of less than 100 °C Provided is an apparatus comprising the same.

Brief Description of the Drawings

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Modes for Carrying Out the Invention

[0016] Polymer feed The polymer feed preferably comprises at least 80% by weight of a polyolefin polymer, for example at least 85% by weight of a polyolefin polymer. Preferably, the polymer feed comprises at least 90% by weight of a polyolefin polymer, preferably at least 95% by weight of a polyolefin polymer, for example at least 99% by weight of a polyolefin polymer. In some examples, the polymer feed consists essentially of a polyolefin polymer, for example a polyolefin polymer having only trace amounts of impurities and having no significant effect on the process or the product formed.

[0017] Preferably, the polymer feed comprises or consists essentially of waste plastics. Sources of such waste materials include bags, bottles, films, sheets, fibers, fabrics, pipes and other molded or extruded forms.

[0018] Thus, other plastic polymers may be present at 20 wt% or less, preferably 10 wt% or less, more preferably 5 wt% or less, such as 1 wt% or less of the polymer feed. Other plastic materials include aromatic plastic polymers such as polystyrene; halogenated plastic polymers such as polyvinyl chloride and polytetrafluoroethylene; and polyester plastic polymers such as polyethylene terephthalate. In some examples, these polymers can cause gum formation, disrupt operation, and require cleaning, so preferably these other polymers are limited in the polymer feed. Halogen-containing polymers can also form hydrohalic acids during pyrolysis, which can cause corrosion problems or require additional processing steps and / or equipment to neutralize or trap the acid.

[0019] As will be appreciated, the polymer feed may, in some examples, contain residual impurities that may be present in waste plastics, such as dirt, paper, such as adhesives and pigments from labels, or metals. Preferably, such impurities are present in the polymer feed in an amount of less than 5 wt%, preferably less than 1 wt%.

[0020] In some embodiments, the method may include removing non-polyolefin polymers and / or non-plastic impurities using, for example, a magnet for removing metals or an optical sorting process, prior to providing the feed to the method.

[0021] Preferably, the polyolefin polymer in the feed comprises or consists essentially of polyethylene and polypropylene. For example, the polyolefin polymer comprises at least 90 wt% polyethylene and polypropylene, preferably at least 95 wt% polyethylene and polypropylene, such as at least 99 wt% polyethylene and polypropylene. The polyethylene can be any form of polyethylene, but preferably comprises or consists essentially of high-density polyethylene (HDPE) and low-density polyethylene (LDPE). Thus, the polymer feed may comprise or consist essentially of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene. In some preferred embodiments, the polyolefin polymer in the feed comprises or consists essentially of polyethylene (such as LDPE and HDPE), for example at least 90 wt% polyethylene, preferably at least 95 wt% polyethylene, such as at least 99 wt% polyethylene. In some preferred embodiments, the polyolefin polymer in the feed comprises at least 40 wt% polyethylene, preferably at least 50 wt% polyethylene.

[0022] Both LDPE and HDPE are polymers of ethylene and have the formula (CH2CH2). n The properties of polyethylene, and thus its classification as LDPE or HDPE and its use, depend on factors such as molecular weight, branching, and density. LDPE preferably has a molecular weight of 30,000 - 50,000 g / mol and a density of 0.910 - 0.925 g / cm. 3 HDPE preferably has a molecular weight of 200,000 - 500,000 g / mol and a density of 0.941 - 0.980 g / cm. 3has a density. LDPE preferably has branches at 1-4% carbon atoms, more preferably 1-3% carbon atoms, and even more preferably 1.5-2.5% carbon atoms. HDPE preferably has fewer branches than LDPE, for example, less than 2% carbon atoms, preferably less than 1% carbon atoms, more preferably less than 0.5% carbon atoms, and even more preferably less than 0.1% carbon atoms. Since LDPE generally has more branches than HDPE, the intermolecular forces between chains are weaker than those of HDPE, the tensile strength is lower, and the elasticity is higher. In contrast, HDPE is known for its high strength-to-density ratio. HDPE is generally used in the production of many items, including plastic bags, plastic bottles, pipes, and containers. LDPE is generally used in parts that require flexibility, such as snap-on lids, trays, and containers, as well as plastic wrap.

[0023] Polypropylene is a polymer of propylene and has the formula (CH(CH3)CH2) n Preferably, the density of polypropylene is 0.895-0.92 g / cm 3 . Polypropylene can have a melting point of 130°C to 170°C depending on its stereoregularity. Generally, the properties of polypropylene may be considered similar to those of polyethylene, but the methyl group improves the mechanical properties and heat resistance. Generally, polypropylene is tough and flexible and has good fatigue resistance. Therefore, polypropylene can be used for hinges. Polypropylene can also be used in applications that require high temperatures, such as medical applications that require the use of an autoclave or kettle.

[0024] In addition, polyethylene and polypropylene may be copolymerized with other monomers. The monomers selected depend on the required properties. For example, PE may be copolymerized with vinyl acetate or acrylate. These copolymers can be used in the foams of the soles of sports shoes, as well as in packaging and sports goods. In particular, polyethylene and polypropylene may be copolymerized. For example, a random copolymer of polypropylene and polyethylene can be used in plastic pipework.

[0025] Polyvinyl chloride (PVC) is a polymer containing chlorine. The main product of PVC pyrolysis is hydrochloric acid (HCl), and the yield of pyrolysis oil is low. The toxic and corrosive nature of HCl not only damages processing equipment but also has an adverse impact on the environment and human health. For these reasons, it is particularly preferred not to use PVC for pyrolysis or to use only a small amount. Such a small amount is ideally less than 0.1% by weight of the polymer feed, preferably less than 0.07% by weight, more preferably less than 0.05% by weight. In order to remove hydrochloric acid that may be present / formed during processing, calcium oxide may be added to the plastic feed material. It will be recognized that the amount of calcium oxide used may vary depending on the amount of the polymer containing chlorine in the polymer feed, such as PVC. Calcium oxide may be added to the plastic feed in an amount of 1% to 5% by weight, preferably 2% to 4% by weight, more preferably 2.5% to 3.5% by weight. Calcium oxide is preferably added to the polymer feed before pyrolysis, for example, before being fed into a kiln. For example, calcium oxide may be added to the polymer feed in a melt extruder before entering the kiln, such as by adding calcium oxide to the hopper that supplies the feed plastic to the melt extruder.

[0026] The polymer feed is preferably melted to provide a molten plastic feed for pyrolysis. The polymer feed may be processed before melting, for example, by extrusion, cutting and / or shearing, to change the shape and / or size of the plastic. The plastic feed may be in the form of pellets, flakes, threads or fibers, films and may be cut. Preferably, the plastic feed is processed to increase the surface area, whereby melting can be assisted.

[0027] For example, following the extrusion of the plastic feed, it is melted, or the molten plastic for pyrolysis in a rotary kiln is conveyed, so that the polymer feed is preferably melted prior to pyrolysis. For example, the melting is preferably carried out in a melt extruder. Alternatively, the polymer feed may be melted at the inlet to the heated rotary kiln or within the melting zone of the kiln in front of the heating zone where pyrolysis occurs. The step of melting the polymer feed may include heating the polymer feed to a temperature of 200 to 400 °C, preferably 250 to 350 °C, more preferably 265 to 325 °C. The melt extruder may preferably include a heated screw extruder that can be heated in any suitable manner, for example, using an electric heater. In other embodiments, the polymer feed may be melted by microwave heating.

[0028] Pyrolysis Pyrolysis of the polymer feed is carried out by providing the molten polymer feed to a plurality of sequential heating zones of a rotary kiln reactor. Rotary kilns are known to those skilled in the art and typically may include a substantially cylindrical (e.g., tube-shaped) reactor configured to rotate about its long axis (i.e., the axis extending along its length through the center of the circular cross-section of the reactor tube). The rotary kiln may have a variety of exact configurations but typically has an inlet at one end of the reactor and an outlet at the opposite end. The molten polymer feed may be supplied to the kiln from the melt extruder by any suitable means, for example, through a suitable transfer pipe. The rotary kiln may be inclined to provide a height difference between its two ends so that the polymer feed and intermediate pyrolysis products (i.e., pyrolysis products formed from the feed, still present in the kiln, and which may or may not undergo further cracking before exiting the kiln) can move under gravity from the inlet to the outlet while the kiln is rotating. The rotation of the kiln is not particularly limited and may rotate, for example, at a speed of 0.1 to 5 rpm, for example 0.1 to 2 rpm.

[0029] Pyrolysis can generally be carried out using any suitable conditions known to those skilled in the art and is carried out by heating the polymer feed in the absence of oxygen. Pyrolysis is preferably carried out under an inert atmosphere, such as nitrogen or argon, preferably nitrogen. Thus, in a preferred embodiment, the rotary kiln is maintained under an atmosphere of an inert gas, preferably nitrogen.

[0030] As described, the rotary kiln includes a plurality of heating zones, preferably four or five or more sequential heating zones, and preferably each heating zone is operated at a higher temperature than the immediately preceding zone. Each heating zone of the rotary kiln is preferably operated at a temperature of 300 °C to 800 °C, and preferably each zone of the rotary kiln is operated at a temperature of 310 °C to 720 °C, such as 400 °C to 670 °C. In a preferred embodiment, the polymer feed undergoes a temperature increase as it passes through the kiln from zone to zone. For example, in a preferred embodiment, four or five or more sequential heating zones include sequential zones that operate from 310 °C to 600 °C in the first zone to 480 °C to 710 °C in the final zone. Preferably, the final zone of the plurality of zones is heated to a higher temperature than the other heating zones. Heating to a higher temperature in the final zone eliminates the need to maintain a high temperature that can cause overcracking of the polymer feed throughout the kiln, reduces the loss of hydrocarbon products containing char, and has been found to increase the processability of the char. In some embodiments, the heating zone may include at least six sequential heating zones. The heating zones suitably include separate discrete heating zones such that each zone is heated to a predetermined temperature and each subsequent zone is heated to a higher temperature. The flow of material through the kiln (i.e., the polymer feed and intermediate pyrolysis products) may be substantially constant along its length. Thus, by varying the length of each heating zone within the kiln, the residence time in each heating zone can be appropriately varied. In some preferred embodiments, each heating zone is of equal length, providing an equal residence time within each zone, but this is not essential.

[0031] The temperature of the zone referred to in this specification is understood to refer to the temperature of the wall of the rotary kiln in each zone, and it will be recognized that the exact temperature of the polymer or pyrolysis material in the reactor can vary.

[0032] By providing a pyrolysis process using the rotary kiln described, lighter C that can itself be used to provide a valuable product stream can be provided. 20 It has been found that light waxes having a melting point of less than 100 °C and that can be easily separated from the liquid fraction of less than C can be produced in high proportions. In particular, surprisingly, the wax fraction produced in this process can be separated from the liquid fraction of less than C in a single step, and the resulting wax fraction does not require the consumption of energy for further fractionation to remove heavier wax fractions and can be separated into various light wax fractions having a melting point of less than 100 °C, preferably 85 °C or less. The wax fraction can be produced from pyrolysis as approximately 40 wt% (suitably 20 - 50 wt%, such as 35 - 45 wt%) of the liquid fraction of the fluid product stream. Thus, the liquid hydrocarbon product stream from the kiln can contain a wax fraction having a melting point of less than 100 °C and a light fraction containing C5 - C 20 hydrocarbons. The wax fraction can advantageously be further separated to provide three separate wax fractions (30 / 40 grade, 50 / 60 grade, and 70 / 80 grade waxes) having freezing points in the ranges of 30 - 40 °C, 50 - 60 °C, and 70 - 80 °C respectively, and the C5 - C 5+ fraction can be processed to produce naphtha and diesel. The use of the rotary kiln advantageously results in the continuous production of these hydrocarbon products, with the polymer feed being continuously supplied to the inlet of the kiln and the products being continuously withdrawn from the outlet. 20+ hydrocarbons. The wax fraction can advantageously be further separated to provide three separate wax fractions (30 / 40 grade, 50 / 60 grade, and 70 / 80 grade waxes) having freezing points in the ranges of 30 - 40 °C, 50 - 60 °C, and 70 - 80 °C respectively, and the C5 - C 20 fraction can be processed to produce naphtha and diesel. The use of the rotary kiln advantageously results in the continuous production of these hydrocarbon products, with the polymer feed being continuously supplied to the inlet of the kiln and the products being continuously withdrawn from the outlet. 20 fraction can be processed to produce naphtha and diesel. The use of the rotary kiln advantageously results in the continuous production of these hydrocarbon products, with the polymer feed being continuously supplied to the inlet of the kiln and the products being continuously withdrawn from the outlet.

[0033] The pyrolysis vessel may be operated at atmospheric pressure (1 atm), for example, approximately 101 kPa. Preferably, the rotary kiln is operated at a slight negative pressure, for example, less than 50 kPa below atmospheric pressure, preferably less than 10 kPa below atmospheric pressure, more preferably less than 0.1 kPa below atmospheric pressure, and most preferably less than 0.01 kPa below atmospheric pressure, for example, maintained at 90 kPa to 101 kPa, or preferably 95 kPa to 101 kPa. Thus, the rotary kiln is preferably operated at a slight negative pressure of approximately atmospheric pressure or above 0.9 bar absolute pressure, for example, above 0.95 bar absolute pressure. As will be appreciated, the pressure within the rotary kiln can be controlled by controlling and balancing the flow, particularly the flow of gas entering and leaving the reactor. In particular, the slight negative pressure within the kiln may simply be the result of withdrawing the product from the outlet of the kiln through the condensation system.

[0034] The residence time in the reactor can be varied by controlling the flow rate of the polymer feed entering the kiln and the flow of the product exiting the kiln, as well as by the configuration of the kiln itself. For example, to provide the desired flow of feed and intermediate pyrolysis products through the kiln, the physical orientation of the kiln (i.e., the degree to which the kiln is inclined from horizontal) and / or the speed of rotation of the kiln may be varied. By using a rotary kiln having a plurality of heating zones in the present method, the residence time of the polymer feed and intermediate pyrolysis products in the kiln and within each heating zone can be advantageously controlled. This allows the method to be easily adapted to vary the product composition, for example, by varying the method in response to changes in the polymer feed, to maintain a constant product composition, or to vary the method to vary the distribution of various products (e.g., the amounts of various hydrocarbon fractions) to meet requirements. As will be appreciated, the residence time may be varied depending on the operating conditions inside the kiln. Preferably, the residence time in the kiln is from 30 minutes to 120 minutes, more preferably from 40 minutes to 70 minutes. As previously discussed, the kiln may include a final zone that is heated to a higher temperature than the preceding zones. Thus, the residence time of the feed inside the kiln may be 30 - 60 minutes, for example 40 - 50 minutes, at a temperature of 310°C - 600°C, and in the final zone 5 - 30 minutes, for example 10 - 20 minutes, at a temperature of 480°C - 710°C. The residence time refers to the time it takes for the molten feed present in the kiln to pass from the inlet to the outlet, although it will be recognized that pyrolysis vapors formed during processing may exit the kiln more rapidly in the gas phase. A flow of an inert gas, preferably nitrogen, is provided at the inlet of the kiln to provide an inert atmosphere and to provide a gas flow for carrying the pyrolysis vapors to the outlet of the kiln.

[0035] The heating of the rotary kiln may be by any suitable means. Preferably, the rotary kiln is an indirectly heated rotary kiln that includes one or more heaters, and the walls of the kiln are heated from the outside to effect heating of the material within the kiln. For example, the kiln may include a rotary kiln surrounded by a furnace or having any suitable heater configured to heat the walls of the kiln. As will be appreciated, the one or more heaters may be separate and arranged to heat each heating zone of the kiln separately, or the one or more heaters may be combined. For example, the heater may include a furnace having a plurality of burners at different points along the length of the kiln, and each burner may be controlled (e.g., by controlling the fuel flow to the burner) to provide a different heating output. In some examples, the furnace may include a common volume surrounding the kiln and a common exhaust outlet for the combustion gases from all the burners. Nevertheless, it will be appreciated that any suitable heater may be provided to heat the heating zones of the kiln.

[0036] The method may preferably include, following the heating zone, a step of cooling and condensing the pyrolysis products. For example, the kiln may include one or more condensers at or connected to the vapor outlet of the kiln. For example, the kiln may include a vapor outlet for providing a gas containing pyrolysis vapors to one or more condensers and a char outlet for receiving solid char from the kiln. The means for cooling and condensing the pyrolysis products may include any suitable condenser or condenser system. Preferably, the one or more condensers may be provided with a gaseous fluid product stream of pyrolysis products from the vapor outlet of the kiln. The fluid product stream may be a vapor stream that may contain a liquid or solid (e.g., fine char particles) as an aerosol, and it will be appreciated that the condenser is configured to provide a liquid fraction along with a non-condensable gas. The one or more condensers may be, for example, C 5+It may include a quench tower configured to condense a liquid fraction containing hydrocarbons, and optionally C remaining in the gaseous effluent from the quench tower 5+ It may include one or more additional condensation stages configured to condense hydrocarbons and optionally to condense and separate an LPG fraction from the gas. Thus, the condensation system for condensing the vapors from the kiln may include a quench tower and preferably a first condensation stage operable at about 50-70 °C and may include, for example, one or more tube and shell condensers and a second condensation stage operable at about 10-30 °C. The non-condensable gas may, in some embodiments, be used to provide fuel for heating the kiln.

[0037] Pyrolysis products Pyrolysis produces a fluid product stream and a solid char product in the kiln, and preferably the pyrolysis products from the kiln consist essentially of the fluid product stream and the char. The fluid product stream typically contains hydrocarbons of a range of different chain lengths, including a liquid fraction containing hydrocarbons and a non-condensable gas fraction. The fluid product stream preferably consists essentially of a non-condensable gas fraction and a liquid fraction containing hydrocarbons, and the non-condensable gas fraction is separated from the liquid fraction prior to the hydrogenation step (v). For example, the non-condensable gas may be appropriately withdrawn from the fluid product stream during condensation, where the fluid product stream is condensed to provide a liquid fraction and the non-condensable gas can be removed. As will be appreciated, the composition of the liquid fraction may depend on the processing conditions and the manner in which the non-condensable gas is separated. For example, in some cases, the liquid fraction may contain a small proportion of lighter hydrocarbons, such as C4 hydrocarbons, but preferably less than 1 wt%, such as less than 0.5 wt% or less than 0.1 wt%. Preferably, the non-condensable gas comprises less than 30 wt%, more preferably less than 25 wt%, such as less than 20 wt% of the fluid product stream. Preferably, C 5+ It contains hydrocarbons of a range of different chain lengths, including a liquid fraction containing hydrocarbons and a non-condensable gas fraction. The fluid product stream preferably consists essentially of a non-condensable gas fraction and a liquid fraction containing hydrocarbons, and the non-condensable gas fraction is separated from the liquid fraction prior to the hydrogenation step (v). For example, the non-condensable gas may be appropriately withdrawn from the fluid product stream during condensation, where the fluid product stream is condensed to provide a liquid fraction and the non-condensable gas can be removed. As will be appreciated, the composition of the liquid fraction may depend on the processing conditions and the manner in which the non-condensable gas is separated. For example, in some cases, the liquid fraction may contain a small proportion of lighter hydrocarbons, such as C4 hydrocarbons, but preferably less than 1 wt%, such as less than 0.5 wt% or less than 0.1 wt%. Preferably, the non-condensable gas comprises less than 30 wt%, more preferably less than 25 wt%, such as less than 20 wt% of the fluid product stream. Preferably, C 5+ It consists essentially of a liquid fraction containing hydrocarbons and a non-condensable gas fraction, and the non-condensable gas fraction is separated from the liquid fraction prior to the hydrogenation step (v). For example, the non-condensable gas may be appropriately withdrawn from the fluid product stream during condensation, where the fluid product stream is condensed to provide a liquid fraction and the non-condensable gas can be removed. As will be appreciated, the composition of the liquid fraction may depend on the processing conditions and the manner in which the non-condensable gas is separated. For example, in some cases, the liquid fraction may contain a small proportion of lighter hydrocarbons, such as C4 hydrocarbons, but preferably less than 1 wt%, such as less than 0.5 wt% or less than 0.1 wt%. Preferably, the non-condensable gas comprises less than 30 wt%, more preferably less than 25 wt%, such as less than 20 wt% of the fluid product stream. Preferably, C 5+The liquid fraction containing hydrocarbons accounts for at least 60% by weight, preferably at least 65% by weight, more preferably at least 70% by weight, for example at least 75% by weight, for example about 80% by weight of the total emissions from the kiln (the total emissions include the liquid fraction, non-condensable gas and char).

[0038] The non-condensable gas may typically contain C1-C4 hydrocarbon gases and in some preferred embodiments is recycled to heat the kiln and / or to heat and melt the polymer feed. In some embodiments, C3 and C4 hydrocarbon gases from the non-condensable gas, as well as C4 gas recovered from the liquid fraction, may be separated and provided as an LPG product stream. Any C present in the non-condensable gas from the condensation, if present 5+ The hydrocarbons may be recovered and combined with the liquid fraction or its downstream product (e.g., the naphtha fraction).

[0039] The solid char product preferably accounts for 15% by weight or less, preferably 10% by weight or less of the emissions from the kiln. The solid char product may in some embodiments contain 10-60% by weight of carbon, for example 20-40% by weight of carbon, which refers to the carbon content of the char itself, and the remainder includes various non-pyrolyzable materials present in the polymer feed, such as inorganic materials and metals, as will be recognized.

[0040] The method preferably includes the step of separating solid char product from the fluid product stream. Such separation can be carried out in any suitable manner known for separating solids from a fluid stream. Most of the char is obtained from the rotary kiln as a solid product stream, and thus is separated from the pyrolysis vapors by providing the char from a char outlet from the kiln, separate from the vapor outlet. Nevertheless, some char may still be present as an aerosol in the vapors exiting the kiln that are condensed. Such residual char in the liquid product may be removed in any suitable manner. Preferably, the condensed fluid product stream is separated from the residual solid char using decanter centrifugation or tricanter centrifugation. For example, the liquid from a condenser, such as a quench tower, may be combined with water and separated by tricanter centrifugation that separates solid char from the pyrolysis oil liquid fraction and water. The liquid fraction may, in some embodiments, be filtered before being sent to a hydrogenation step to remove any residual solids.

[0041] Since the rotary kiln can continuously remove char from the reactor (e.g., as compared to a stirred tank reactor, etc.), the method does not need to stop the process to remove solid residues, such as char or other non-volatile residues, from the reactor and can operate continuously. This allows the method to also continuously run to provide the desired range of hydrocarbon products without the need (as in a tank reactor, etc.) to remove the char product to avoid downtime and cleaning.

[0042] C 5+The liquid fraction from the kiln containing hydrocarbons may have a freezing point in the range of, for example, 40°C to 60°C, such as 45°C to 55°C (for example, 60°C or less, or 55°C or less), and / or a density of 0.6 g / ml to 0.9 g / ml, such as 0.7 g / ml to 0.8 g / ml. Depending on the polymer feed to the kiln, the liquid hydrocarbon fraction may suitably contain sulfur at a concentration of less than 30 mg / kg (measured by ASTM D5453-19a), although in some instances the sulfur concentration can be at least 5 mg / kg or at least 10 mg / kg. Depending on the feed composition and any steps taken to remove chlorine (such as in PVC) from the feed, the liquid hydrocarbon fraction may contain chlorine at a concentration of less than 100 mg / kg (measured by UOP 779-08), preferably less than 80 mg / kg, although in some instances the chlorine concentration can be at least 10 mg / kg, or at least 40 mg / kg, such as at least 60 mg / kg. It will be appreciated that in some instances such impurities may be reduced by treating or controlling the composition of the polymer feed prior to pyrolysis. The liquid hydrocarbon fraction from the kiln may have a bromine index of, for example, 10 to 50 gBr / 100 g, preferably 10 to 30 gBr / 100 g, such as 15 to 25 gBr / 100 g.

[0043] Hydrogenation C from the kiln 5+ The liquid fraction of the fluid product stream containing hydrocarbons is hydrogenated to provide a hydrogenated product stream. Suitably, C 5+ The entire liquid fraction of the fluid product stream containing hydrocarbons (i.e., all of the pyrolysis products excluding char and non-condensable gases) is sent to a hydrogenation reactor and hydrogenated to produce a hydrogenated hydrocarbon product stream.

[0044] Hydrocarbon streams containing those derived from the pyrolysis of plastics may typically contain various heteroatoms, such as N, S, O, as impurities, which may adversely affect the properties of the hydrocarbon products. The pyrolysis of polyolefin plastics also typically produces a mixture of olefins and saturated hydrocarbons. Olefins and heteroatom-containing hydrocarbons are more chemically reactive than paraffins. By performing hydrogenation of the entire liquid fraction of the fluid product stream from the kiln prior to further fractionation or processing steps, side reactions of olefins or heteroatom-containing hydrocarbons, such as polymerization, can advantageously be avoided. In addition, since the boiling points of olefin and heteroatom-containing hydrocarbon molecules change compared to saturated hydrocarbons, the presence of heteroatom-containing molecules and olefins may then be more cleanly separable depending on the carbon number.

[0045] Hydrogenation can be carried out in any suitable manner, preferably including contacting the liquid fraction of the fluid product stream with a hydrogenation catalyst and hydrogen gas at a temperature of 250 °C to 400 °C, preferably 250 °C to 350 °C. Due to the exothermic hydrogenation reaction, it will be recognized that the temperature can appropriately rise from the inlet to the outlet of the hydrogenation reactor. Therefore, the catalyst bed in the hydrogenation reactor can have a temperature variation of 250 °C to 400 °C, preferably 250 °C to 350 °C. The pressure in the hydrogenation reactor can preferably be 3 MPa to 10 MPa, preferably 4 MPa to 6 MPa (in some examples, the pressure can be higher, such as up to 20 MPa). The liquid hourly space velocity (LHSV) of the fluid product stream passing through the reactor can be 0.5 kg / kg / hr to 10 kg / kg / hr, preferably 0.5 kg / kg / hr to 4 kg / kg / hr, more preferably 0.7 kg / kg / hr to 2.5 kg / kg / hr, most preferably 0.8 kg / kg / hr to 1.5 kg / kg / hr, for example 0.9 kg / kg / hr to 1.3 kg / kg / hr. The ratio of hydrogen gas to the feed liquid in hydrogenation can appropriately be 300 NV / NV to 1000 NV / NV, preferably 400 NV / NV to 600 NV / NV, for example 450 NV / NV to 550 NV / NV. The hydrogen consumption during the hydrogenation step varies based on the feed to the hydrogenation reactor and other conditions, but can be, for example, in the range of 6 - 12 gH2 / kg, for example 8 - 10 gH2 / kg.

[0046] Hydrogenation can be carried out in any suitable reactor for contacting the liquid fraction with hydrogen gas. Preferably, the hydrogenation reactor includes a fixed bed reactor. The aspect ratio of the fixed bed reactor can be any suitable ratio, such as 5:1 to 20:1, preferably 8:1 to 16:1, for example 10:1 to 14:1, for example about 12:1. The hydrogenation reactor is preferably a trickle bed reactor. In some embodiments, the hydrogenation reactor can alternatively be a fluidized bed reactor or a microchannel reactor.

[0047] The hydrogenation catalyst may be any suitable catalyst, preferably a metal catalyst. The metal hydrogenation catalyst preferably contains a metal selected from Group VIII of the periodic table. Preferably, the catalyst contains Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and / or Pt. For example, the catalyst contains Ni, Co, Mo, W, Cu, Pd, Ru, Pt. In a preferred embodiment, the catalyst is selected from CoMo, NiMo, or Ni, preferably NiMo. The hydrogenation catalyst is preferably supported on a carrier such as bauxite, alumina, silica, silica-alumina, or zeolite. Preferably, the catalyst is supported on alumina. For example, the hydrogenation catalyst may include NiMo supported on alumina (NiMo / Al2O3).

[0048] The hydrogenation reactor may include a gas recirculation loop for recycling hydrogen passing through the reactor. Hydrogenation preferably includes hydrodesulfurization, and the gas-phase H2S concentration in the reactor can be 0.05% - 0.5%, for example, about 0.1%. In some embodiments, H2S can be introduced into the recirculation gas by passing the CS2 liquid at ambient temperature and reaction pressure.

[0049] In some preferred embodiments, the hydrogenation includes providing the hydrogenation effluent to a second hydrogenation stage that can be carried out under substantially the same conditions as the first hydrogenation step. The second hydrogenation step can, in some instances, be carried out at an initial temperature higher than the first hydrogenation step, but due to the low heat of reaction, the temperature can still preferably be in the range of 250 °C to 350 °C, preferably 300 °C to 350 °C. The second hydrogenation step can be carried out with a longer contact time, for example, at a lower liquid hourly space velocity than the first hydrogenation step. The second hydrogenation step has been found to have a minimal effect on heteroatom removal, but advantageously can reduce the presence of olefins in the hydrogenation product stream. In some embodiments, the first and second hydrogenation steps may include a combined hydrogenation step corresponding to carrying out the first hydrogenation step and the second hydrogenation step continuously. For example, a single hydrogenation step with an increased contact time through the catalyst bed, or preferably a single hydrogenation step with two catalyst beds containing different catalysts with different activities, can be used by lengthening the catalyst bed or reducing the flow rate of the feed through the reactor. In such a hydrogenation step, the hydrogen consumption during the hydrogenation step can be, for example, at least 9 g H2 / kg.

[0050] After the hydrogenation step, the hydrogenated hydrocarbon product stream can have a freezing point in the range of, for example, 40°C to 60°C, for example 50°C to 60°C, for example 60°C or less. The freezing point referred to herein can be measured in accordance with ASTM D938-12 (2017). The hydrogenated hydrocarbon product stream can have a density of 0.7 g / ml to 0.9 g / ml, for example 0.75 g / ml to 0.85 g / ml. Depending on the hydrogenation conditions and the sulfur content of the feed to the hydrogenation, the hydrogenated hydrocarbon product stream can contain sulfur at a concentration of less than 15 mg / kg (measured by ASTM D5453-19a), preferably less than 10 mg / kg, more preferably less than 5 mg / kg, for example less than 2 mg / kg. Depending on the hydrogenation conditions and the chlorine content of the feed to the hydrogenation, the hydrogenated hydrocarbon product stream can contain chlorine at a concentration of less than 15 mg / kg (measured by UOP 779-08), preferably less than 10 mg / kg, for example less than 5 mg / kg, or less than 2 mg / kg. The hydrogenated hydrocarbon product stream preferably has a bromine index of less than 2 gBr / 100 g, preferably less than 1 gBr / 100 g, for example less than 0.7 gBr / 100 g, for example 0.5 gBr / 100 g or less. As will be appreciated, the hydrogenation conditions can be selected to provide the bromine index described above, and / or the levels of sulfur and / or chlorine. Thus, if necessary, the hydrogenation conditions can be adjusted to increase the contact time, to increase the ratio of hydrogen gas to feed liquid, or to use a more active catalyst.

[0051] Fractionation of the hydrogenated hydrocarbon product stream The method includes fractionating the hydrogenated hydrocarbon product stream to produce a wax fraction having a melting point of less than 100°C, preferably less than 85°C, more preferably less than 75°C (the melting point of the wax referred to herein can be measured in accordance with ASTM D127-19). Alternatively or in addition, the 20+ wax fraction can have a freezing point of less than 100°C, preferably less than 85°C, more preferably less than 75°C. The 20+ wax fraction can, in some examples, contain a small amount of approximately 20+ C 18It will also be appreciated that hydrocarbons lighter than may be included. However, the C 20+ wax fraction preferably contains hydrocarbons less than 15 wt%, such as less than 10 wt%, preferably less than 5 wt%, of C 20 hydrocarbons or products boiling below 350 °C. In some embodiments, the C 20+ wax fraction may contain less than 2 wt%, preferably less than 1 wt% of products boiling below 350 °C, for example the C 20+ wax fraction preferably consists essentially of C 20+ hydrocarbons. Preferably, the C 20+ wax fraction having a melting point below 100 °C comprises 30 to 50 wt%, preferably 35 to 45 wt% of the hydrogenated hydrocarbon product stream. Thus, the process can operate to produce the C 20+ wax fraction as less than half of the liquid product from the kiln, which advantageously provides a wax fraction that can conveniently be separated to provide light wax without the need for energy intensive separation of heavier wax fractions. The remaining C 5-20 liquid fraction of the hydrogenated hydrocarbon product stream can also conveniently be processed to provide gas oil and naphtha.

[0052] Thus, in the process it is desired to produce the C 20+ wax fraction, but surprisingly, the C 20 fraction of the fluid product stream containing hydrocarbons less than and overall less wax than may typically be produced in wax production processes, can be produced and hydrogenated to achieve an increase in the efficiency of the light C 5+ wax. The hydrogenated hydrocarbon product stream is then fractionated to obtain a C 20+ wax fraction and a C 20+ liquid hydrocarbon fraction. Due to the difference in boiling points of olefins and heteroatom-containing species compared to paraffins as discussed previously, performing the fractionation step after hydrogenation results in some of the C 5-20 wax being lost to the light fraction (or the C 20+ wax fraction being lost to the light fraction (or the C20 Avoidance of contamination of the wax fraction with hydrocarbons below C 20+ can be assisted. Without wishing to be bound by any particular theory, following controlled pyrolysis in a rotary kiln, the method including hydrogenation of the effluent from the kiln can produce light waxes without the need for fractions from heavier wax fractions, saving energy and reducing yield losses by minimizing the number of required fractionations, producing hydrocarbon distributions that are advantageously distributed.

[0053] Fractionation can be carried out using any suitable fractionation means, such as a fractionation column, or by fractional condensation. Preferably, the step of fractionating the hydrogenated hydrocarbon product stream includes fractionation in a fractionation column.

[0054] Fractionation may preferably include providing the hydrogenated hydrocarbon product stream to a vacuum distillation system. Fractionation may include using, for example, a reboiler equipped with a jet spray evaporation device and a forced flow mechanism configured to improve the evaporation efficiency and heat exchange of the liquid in the reboiler, and configured to improve the evaporation of the liquid.

[0055] The evaporation temperature of the liquid in the fractionation (e.g., the liquid exiting the reboiler) can be 260°C to 320°C, preferably 270°C to 300°C, for example 280°C to 290°C. It has been found that minimization of the decomposition of the hydrocarbonaceous product stream can be achieved under such conditions. The evaporation output can be, for example, 0.5 kW to 2 kW, for example 0.9 kW to 1.3 kW. The evaporation pressure can be 3 to 8 kPa absolute (e.g., the pressure above the liquid in the reboiler), preferably 4 to 6 kPa absolute. Condensation of the evaporation product can be carried out by cooling to approximately less than 25°C, for example about 20°C. The hydrocarbonaceous product stream can be fed to the fractionation at a temperature of, for example, 60°C to 300°C, for example 70°C to 200°C, for example 80°C to 120°C, for example approximately 100°C. The reflux rate in the fractionation can be, for example, 0.5 l / hr to 2 l / hr, for example 0.8 l / hr to 1.2 l / hr. The vacuum system may suitably include a cold trap, for example a cold trap at approximately -78°C or below, to prevent loss of light components.

[0056] Treatment and Separation of Wax C after fractionation 20+ The wax fraction can preferably have a freezing point of 60 to 70°C (measured by ASTM D938-12 (2017)). Preferably, C 20+ The wax fraction may have a sulfur content of less than 15 mg / kg, preferably less than 10 mg / kg (measured by ASTM D5453-19a). C 20+ The bromine index of the wax is preferably less than 1 gBr / 100 g, more preferably less than 0.5 gBr / 100 g.

[0057] In some embodiments, C 20+ The wax fraction is decolorized. For example, C 20+ The wax fraction may be decolorized by hydrotreating with hydrogen gas in a fixed bed reactor. The conditions applied are, for example, substantially those of the pyrolysis product C 5+As previously shown herein with respect to the hydrogenation of liquid fractions, a temperature of 300 - 350 °C may be used and a NiWMo / Al2O3 catalyst may be used. However, it will be appreciated that any suitable decolorization method may be used. Decolorization, if carried out, should be carried out appropriately such that the freezing point (and / or density) of the material remains substantially unchanged and thus has a minimal effect on the wax composition.

[0058] Preferably, the method comprises fractionating the C 20+ wax fraction to produce two or more separate wax fractions each having a melting point (and / or freezing point) of less than 100 °C, preferably 85 °C or less, such as 80 °C or less. As discussed previously, by use of the method, C from pyrolysis and hydrogenation 20+ It has been found that the wax fraction can be fractionated into different light wax fractions without the need to separate from heavier waxes (e.g., having a melting point and / or freezing point of 100 °C or more, preferably 85 °C or more, more preferably 80 °C or more).

[0059] Preferably, the C 20+ wax fraction is fractionated to provide at least two, preferably three, separate wax fractions each having a freezing point in the range of 30 - 40 °C, 50 - 60 °C and / or 70 - 80 °C.

[0060] It will be appreciated that the fractionation in step (vii) of the method may be carried out in any suitable manner. Preferably, the C 20+ means for fractionating the wax fraction comprises one or more thin film evaporators which, in a preferred embodiment, are each configured to provide three separate wax fractions having freezing points in the range of 30 - 40 °C, 50 - 60 °C and 70 - 80 °C.

[0061] Separate wax fractions may be formed by sequential fractionation steps, for example using fractionators arranged in series. By way of example, the C 20+When fractionating the wax fraction to provide three separate wax fractions, the first fraction may be configured to provide the first wax fraction as a light product and send the heavy product to the second fraction. At this time, the second fraction may be configured to provide the second wax fraction as a light product and the third wax fraction as a heavy product. The first fraction may be operated, for example, at a temperature of 140 to 170 °C, preferably 150 to 160 °C, and a pressure of 40 to 75 Pa absolute pressure, preferably 50 to 65 Pa absolute pressure. The second fraction may be operated, for example, at a temperature of 250 to 300 °C, preferably 260 to 280 °C, and a pressure of 20 to 60 Pa absolute pressure, preferably 25 to 45 Pa absolute pressure. Although this example only refers to three fractions, it will be recognized that it can also be applied to provide four or more fractions as needed.

[0062] In some examples, a portion of the light fraction from one stage of the fractionation may be sent to a previous stage to improve the separation efficiency. Additionally, the heavy fraction recovered from the last fraction may be separated, if necessary, from residual solids in the wax, such as residual char or other decomposition products or impurities, for example using centrifugation.

[0063] C 20+ If the wax fraction contains hydrocarbons less than C 20 and / or components boiling below 350 °C, if necessary, these may be separated together with the first light fraction of the wax fraction, and then fractionated appropriately to remove hydrocarbons less than C 20+ and / or components boiling below 350 °C. Nevertheless, the product with hydrocarbons less than C 20 and / or boiling below 350 °C is preferably substantially separated from the wax fraction in the first fraction of the hydrocarbon hydrogenation product stream. 20 20+ 20+ 20+

[0064] C 20+Following the fractionation of the wax fraction, one or more fractions may, in some embodiments, be subjected to decolorization, and instead of or in addition to, may be decolorized prior to the previously described fractions. Decolorization may be carried out under substantially the same conditions as previously described, and in some instances, at a lower temperature than previously described decolorization, for example, approximately 260 to 300 °C.

[0065] C 20+ One or more fractions of the wax can be processed to obtain a pelletized wax product, for example, by pelletizing the wax product.

[0066] This method relates to producing wax, but from a hydrogenated hydrocarbon product stream separated (C 20+ to produce a wax fraction)C 5-20 It will be recognized that the light hydrogenated fraction may also be processed to provide useful products. For example, further processing of the light hydrogenated C 5-20 fraction is to C 5-20 hydrocrack the fraction to C 5-10 produce a hydrocarbon-enriched C 5-20 hydrocarbon product stream. The C 5-20 fraction typically has too low a concentration of naphtha-range hydrocarbons to efficiently separate the naphtha fraction. Therefore, by hydrocracking, a naphtha (C 5-10 ) component and gas oil (C 10-20)A mixture with components can be provided. The hydrocracking step can be carried out in any suitable manner using any suitable hydrocracking reactor known in the art. For example, the hydrocracking step can be carried out in a fixed-bed reactor, such as a trickle-bed reactor, which may be an isothermal reactor. The hydrocracking catalyst can be any suitable catalyst, but is preferably a metal catalyst supported on a carrier, particularly a sulfur-based hydrocracking catalyst, such as a catalyst supported on zeolite such as bauxite, alumina, silica, silica-alumina or zeolite, preferably USY or mordenite zeolite, and containing Ni, Co, Mo, W, Cu, Pd, Ru, Pt, preferably NiMo or Pt. The hydrocracking step may include contacting the light hydrocracked C 5-20 fraction with the hydrocracking catalyst at a temperature of 250 °C to 400 °C, preferably 300 to 350 °C. Preferably, the hydrocracking step is carried out at a pressure of 3 to 10 MPa, preferably 4 to 8 MPa, such as 5 to 7 MPa. The liquid hourly space velocity (LHSV) of the light hydrocracked fraction through the hydrocracking reactor is 0.5 hr -1 ~5 hr -1 Preferably, it is 0.5 hr -1 ~3 hr -1 More preferably, it is 0.7 hr -1 ~2 hr -1 Most preferably, it is 0.8 hr -1 ~1.5 hr -1 For example, it can be 0.9 hr -1 ~1.3 hr -1 The ratio of hydrogen gas to the feed liquid in the hydrogenation can suitably be 100 NV / NV to 500 NV / NV, preferably 150 NV / NV to 250 NV / NV, such as 180 NV / NV to 220 NV / NV. The H2S level in the reactor can be approximately 500 to 1500 ppm, such as 800 ppm to 1200 ppm, such as about 1000 ppm. The sulfur level can suitably be maintained using CS2 mixed with the feed to the hydrocracking reactor. C from the hydrocracking step 5-20The hydrocarbon product stream may be fractionated to produce a naphtha fraction and a light oil fraction (and optionally washed with water and / or treated with an H2S adsorbent prior to fractionation). The naphtha fraction suitably contains C 5-10 hydrocarbons, preferably at least 90 wt% C 5-10 hydrocarbons, preferably at least 95 wt% C 5-10 hydrocarbons, e.g., at least 98 wt% C 5-10 hydrocarbons. The light oil fraction suitably contains C 10-20 hydrocarbons, preferably at least 90 wt% C 10-20 hydrocarbons, preferably at least 95 wt% C 10-20 hydrocarbons, e.g., at least 98 wt% C 10-20 hydrocarbons. The fractionation of the C 5-20 hydrocarbon product stream can be carried out using any suitable apparatus, such as a distillation column with a reboiler, known in the art.

[0067] Thus, the process can produce, in addition to the wax product, a naphtha fraction and a light oil fraction, which can each be provided for downstream use or further processing into other products. In some embodiments, the process includes recycling the light oil fraction from the fractionation of the C 5-20 hydrocarbon product stream and providing it to the hydrocracking step along with the light hydrogenated C 5-20 fraction to produce a wax and a naphtha fraction. Thereby, the light oil fraction separated from the naphtha fraction can be recycled until it is fully hydrocracked to become a naphtha fraction species. In this way, the process can operate to produce wax and naphtha, surprisingly, with minimal loss of intermediate light oil fraction hydrocarbons. Indeed, by operating the process in this way, surprisingly, it is possible to provide the advantageous production of both wax and naphtha by operating a pyrolysis process that produces a liquid effluent containing a large proportion (e.g., more than 50 wt%) of light oil hydrocarbons.

[0068] Unless otherwise specified or apparent from the context, as used herein Cx-y When referring to a fraction, it will be appreciated that the fraction contains at least 70% by weight, preferably at least 80% by weight, more preferably at least 90% by weight, such as at least 95% by weight, such as at least 98% by weight of the hydrocarbons included in the stated range. In some preferred embodiments, C x-y The hydrocarbon fraction can consist essentially of hydrocarbon molecules having from x to y carbon atoms.

[0069] For reference, unless otherwise specified or unless it is clear that the opposite meaning is intended, all percentages referred to in this application in relation to concentration are in percent by weight (wt%).

[0070] The method of the present invention can be carried out using the features of the various apparatuses described herein, and it will be appreciated that the apparatuses can be configured to carry out the processing steps described herein.

[0071] The present invention will be further described by way of the following examples, which are provided for illustrative purposes and are in no way intended to limit the scope of the claimed invention, and with reference to the following figures. [Examples]

Examples

[0072] Pyrolysis Waste plastic feeds containing HDPE, LDPE and polypropylene were melted in a melt extruder and the molten feed stream was provided to the inlet of a rotary kiln. The feed stream contained calcium oxide to avoid corrosion due to the formation of HCl from any PVC not removed in the feed. The melt extruder was a screw extruder and was heated by an electric heater.

[0073] The rotary kiln included a rotating stainless steel drum having a length of about 80 feet (24.3 m) and an inner diameter of about 6 feet (1.8 m). The drum was rotated at a speed of 0.1 - 2 rpm and operated at a pressure slightly below atmospheric pressure under a nitrogen atmosphere. The rotary kiln was heated in four sequential heating zones of equal length, with the first three zones operating at temperatures of 315°C - 595°C and the last heating zone operating at 480°C - 705°C. The heating of the kiln was carried out by inducing combustion gas into an external jacket surrounding the rotating drum, which was divided into compartments to control the heating of each heating zone by burning natural gas. The residence time in the kiln was 60 minutes, i.e., 45 minutes in the first three zones and 15 minutes in the last zone.

[0074] The emissions from the rotary kiln were char, as well as C 5+ a hydrocarbon liquid fraction and non - condensable gases (C 1-4 hydrocarbon gas and nitrogen - containing) containing a fluid product stream. The fluid product stream was withdrawn from the kiln in the vapor phase through an evaporate outlet and sent to a condensation system, while the char was collected from a divided char outlet configured to receive solids from the kiln.

[0075] The C of the fluid product stream 5+The hydrocarbon liquid fraction was separated from the non-condensable gas in the condensation system, and a portion of the non-condensable gas was sent for fuel heating of the rotary kiln. The condensation system included a quench tower and tube and two tube and shell condensers arranged in series to receive the gas from the quench tower. The fluid product stream was provided to the quench tower above the liquid sump and then drawn up through four spray headers. The liquid was pumped out from the liquid sump of the quench tower, cooled through a cooling heat exchanger (cooled to 60 °C), and then sent to the spray headers. The spray headers of the quench tower were configured to spray in countercurrent to cool the evaporate rising through the tower into condensate, and then the liquid fell into the liquid sump. The spray also functions to wash off the entrained char and prevent it from moving as an aerosol to the operation of the downstream unit. The flow of the cooled liquid from the quench tower was mixed with water, separated by tricanter centrifugation to remove the entrained char and other solid impurities, and then the oil phase was returned to the quench tower or sent downstream for hydrogenation. Any gas not condensed in the quench tower could be passed through the tube and shell condenser. The first condenser was operated at about 20 °C and was configured to provide condensate spraying for removing the entrained char from the first condenser and the pipeline between the quench tower and the condenser. The condensate from the first condenser was provided for hydrogenation together with the liquid from the quench tower. The condensate from the second tube and shell condenser (operated at about 10 °C) could be sent for hydrogenation together with other liquids or combined with the naphtha fraction downstream. C 5+ The hydrocarbon liquid fraction can be stored in an intermediate storage tank configured to receive the liquid from the condensation system and send the liquid to the hydrogenation reactor.

[0076] C condensed from the pyrolysis evaporate of the kiln 5+ The hydrocarbon liquid fraction was found to have the following characteristics. Freezing point: 52 °C Density (60 °C): 0.779 g / ml Bromine index: 20 gBr / 100 g Sulfur (ASTM D5453-19a): 22 mg / kg Chlorine (UOP 779-08): 79 mg / kg Silicon (ASTM D5185-18): 6 mg / kg Metal (ASTM D5185-18): less than 1 mg / kg Note: a. The metals tested include Cr, Cu, Pb, Ni, Zn, Mn, Cd, As, Co, and Sb. b. The detection limit of the ICP of the analytical institution was 1 mg / kg.

[0077] C 5+ Perform simulated distillation of the hydrocarbon liquid fraction and show the results in Figure 1. C 5+ The carbon number distribution determined by gas chromatography (GC) in the hydrocarbon liquid fraction is shown in Figure 2. As can be seen, the pyrolysis products contain a significant proportion (approximately 60 wt%) of gas oil range or lower (boiling point up to about 350 °C) hydrocarbons. The analysis also shows that the pyrolysis products contain hydrocarbons within the naphtha range in a very small proportion (less than 2 wt%). The GC analysis of the products showed the presence of various isomers and n-paraffins in addition to olefins and small amounts of other hydrocarbon species. 5-8 The GC analysis of the products showed that the pyrolysis products contain hydrocarbons within the naphtha range in a very small proportion (less than 2 wt%). The GC analysis of the products showed the presence of various isomers and n-paraffins in addition to olefins and small amounts of other hydrocarbon species.

Example

[0078] Hydrogenation All of the hydrocarbon liquid fractions from Example 1 were sent to a fixed-bed hydrogenation reactor having a catalyst bed aspect ratio of 12:1 and containing a NiMo / Al2O3 hydrogenation catalyst. The temperature setting at the inlet of the reactor was 260 - 270 °C and the pressure was 5.0 MPa. The feed was at 1.1 h 5+ All of the hydrocarbon liquid fractions from Example 1 were sent to a fixed-bed hydrogenation reactor having a catalyst bed aspect ratio of 12:1 and containing a NiMo / Al2O3 hydrogenation catalyst. The temperature setting at the inlet of the reactor was 260 - 270 °C and the pressure was 5.0 MPa. The feed was at 1.1 h -1The LHSV was obtained at 500 NV / NV of hydrogen gas to feed ratio. The gas-phase H2S concentration was approximately 0.1%. A portion of the recycle gas was introduced by skimming through a CS2 liquid at ambient temperature and reaction pressure. The temperature at the reactor outlet was approximately 350 °C, providing a temperature increase of approximately 90 °C through the reactor. Hydrogen consumption was about 8.2 g H2 / kg. During hydrogenation, C 3-4 (LPG) gas or C 1-2 gas, no significant feed cracking was observed.

[0079] The hydrogenated product was found to have a bromine index of 2 g Br / 100 g. Therefore, the initial temperature at the reactor inlet was 305 °C, the outlet temperature was 330 °C, and the LHSV was 0.7 h -1 . The hydrogenated product was sent to a second equivalent hydrogenation. The product recovery over the two hydrogenation steps was greater than 95%.

[0080] The product hydrogenated twice was analyzed and had the following properties. Freezing point: 54 °C Density (60 °C): 0.806 g / ml Bromine index: 0.5 g Br / 100 g Sulfur (ASTM D5453-19a): 14 mg / kg Chlorine (UOP 779-08): 12 mg / kg Silicon (ASTM D5185-18): 6 mg / kg Metal (ASTM D5185-18): less than 1 mg / kg Note: The metals tested included Cr, Cu, Pb, Ni, Zn, Mn, Cd, As, Co, Sb, Mo, Al.

[0081] By GC, the hydrogenated product was also found to substantially contain no olefins observed prior to hydrogenation.

[0082] The simulated distillation of the hydrogenated product was carried out, and the results compared with the crude product before hydrogenation are shown in Figure 3. As can be seen in Figure 3, the boiling point of the hydrogenated product (denoted as O) increased relative to the crude material before hydrogenation (denoted as X). C 20+ In the boiling point range of 350 °C where wax is separated from the lighter liquid fraction, it can be seen that hydrogenation reduces the proportion of materials boiling below 350 °C, and by carrying out hydrogenation of the entire liquid effluent of the kiln before separation, hydrocarbons that would otherwise have been lost in the light fraction C 20+ The increased portion of hydrocarbons indicates that it can be retained together with the wax fraction after fractionation. In particular, when producing light wax, it is advantageous to avoid loss of the light hydrocarbon wax component. 20+

Example

Example

[0083] Fractionation The hydrogenated product was then fractionated in a single cut to obtain a light hydrogenated C 5-20 hydrocarbon fraction and a C 20+ wax fraction. The fractionation was carried out in a distillation column using vacuum distillation. The distillation system included a reboiler equipped with a jet spray evaporation device and a forced flow mechanism to improve the evaporation efficiency and heat exchange of the liquid in the reboiler. The distillation was operated under the following conditions. Evaporation temperature (liquid exiting the reboiler): ~275 °C Evaporation pressure (above the liquid in the reboiler): 4 - 6 kPa (absolute pressure) Evaporation output: ~1.1 kW Cooling water temperature: ~20 °C Pressure at the condenser outlet: ~1 kPaA Sample liquid (approx. 100 °C) feed rate: 2 - 2.5 kg / hr Reflux rate: ~1 liter / hr (Cooling trap temperature of the vacuum pump): -78 °C

[0084] By distillation, a light hydrogenated C 5-20 hydrocarbon fraction and a C 20+ wax fraction were produced. C20+ The wax fraction was found to contain a portion of hydrocarbons of the length of light oil (mostly C 18 and C 19 ), and therefore, preferably, to compensate for this, the temperature of the reboiler may be increased, for example, to approximately 285 °C or higher.

[0085] C 20+ The wax fraction was analyzed as follows. Density (80 °C): 0.810 g / ml Bromine index: less than 0.5 g Br / 100 g Freezing point: 65 °C Sulfur (ASTM D5453-19a): 9.2 mg / kg

[0086] C 20+ A simulated distillation of the wax fraction was performed and the results are shown in Figure 5. C 20+ The carbon number distribution determined by gas chromatography (GC) in the wax fraction is shown in Figure 4. C 20+ The wax fraction was found to contain hydrocarbons in an advantageous distribution for producing three separate wax fractions with relatively low melting point waxes, having freezing points in the ranges of 30 - 40 °C, 50 - 60 °C, and 70 - 80 °C, respectively.

[0087] C 20+ The wax fraction was decolorized in a fixed bed before fractionation according to the following conditions. Catalyst: NiWMo / Al2O3 Aspect ratio of the catalyst bed: 12:1 Reactor temperature (set at the inlet): 320 °C Reactor temperature (measured at the outlet): 320 °C Reaction pressure: 5.0 MPa Liquid hourly space velocity: 1.0 kg / kg / hr Hydrogen gas to feed liquid ratio: ~500 NV / NV Vapor phase H2S concentration: ~0.1%

[0088] C 20+ The density and freezing point of the wax fraction did not change upon decolorization.

Example

[0089] Fractionation of wax C from Example 3 20+ The wax fraction (69.5 kg) was successively separated by fractionation using a thin-film evaporator.

[0090] The first separation (performed at a temperature of 155 °C, a pressure of 55 - 60 Pa absolute pressure, and a feed rate of 2.8 kg / hr) produced a first light fraction, which was further fractionated to remove light oil range hydrocarbons to obtain a 30 / 40 wax product having a freezing point of 35 °C. As will be appreciated, light oil range hydrocarbons may preferably be removed instead during the separation of Example 3. The first heavy fraction from the first separation was provided to a second separation (performed at a temperature of 270 °C, a pressure of 30 - 40 Pa absolute pressure, and a feed rate of 2.5 - 3 kg / hr) to produce a second light fraction having a freezing point of 55 °C (providing a 50 / 60 wax product) and a second heavy fraction having a freezing point of 77 °C (providing a 70 / 80 wax product). Analysis of these wax fractions is shown in Table 1.

Table 1

[0091] Figure 6 schematically shows the process flow of a system for carrying out the method. The polymer feed is pyrolyzed in the rotary kiln reactor 2, and the fluid effluent from the kiln containing all of the agglomerative liquid from the pyrolysis is provided to the hydrogenation reactor 4. The hydrogenated hydrocarbon stream from the reactor 4 is sent to the fractionation stage 6 to obtain 20+ wax fraction 10 and C 5-20 hydrocarbon fraction 8 (light oil / naphtha fraction). C 20+The wax fraction 10 is provided to a first wax fractionation stage 12 (including a thin film evaporator), from which a first light fraction 14 is obtained. The first light fraction 14 is provided as a 30 / 40 wax stream 16 having a freezing point of 30 to 40 °C, and optionally a part 15 of the first light fraction may be recycled to the fractionation stage 6 to improve the removal of the light oil / naphtha fraction components. The first heavy fraction 18 from the first wax fractionation stage 12 is provided to a second wax fractionation stage 20 (including a thin film evaporator), from which a second light fraction 22 is obtained. The second light fraction 22 is provided as a 50 / 60 wax stream 24 having a freezing point of 50 to 60 °C, and optionally a part 23 of the second light fraction may be recycled to the first wax fractionation stage 12. The second heavy fraction 26 from the second wax fractionation stage 20 provides a 70 / 80 wax stream, and optionally residual solids, such as char or other solid impurities 30, may be separated using a solid / liquid separator 28, including, for example, centrifugation.

Claims

1. A method for producing a wax having a melting point of less than 100 °C from a polymer feed, comprising: (i) preparing a polymer feed comprising at least 80% by weight of a polyolefin polymer; (ii) melting the polymer feed to prepare a molten polymer feed; (iii) feeding the molten polymer feed to a rotary kiln reactor comprising a plurality of sequential heating zones, each zone of the rotary kiln being operated at a temperature of 300 °C to 800 °C to pyrolyze the molten polymer feed and produce a fluid product stream and a solid char product; (iv) separating the solid char product from the fluid product stream. (v) C ５＋ Sending the liquid fraction of the fluid product stream containing hydrocarbons to a hydrogenation reactor and hydrogenating the liquid fraction to produce a hydrogenated hydrocarbon product stream (vi) fractionating the hydrogenated hydrocarbon product stream to produce a C wax fraction having a melting point of less than 100 °C ２０＋ step of producing (vii)the foregoing C ２０＋ fractionating the wax fraction to produce two or more separate wax fractions, each having a melting point of less than 100° C The method as described above.

2. The method according to claim 1, wherein the step of fractionating the hydrogenated hydrocarbon product stream comprises fractionating in a fractionation column.

3. The method according to claim 1 or 2, wherein the rotary kiln comprises four or five or more sequential heating zones.

4. The method according to any one of claims 1 to 3, wherein the rotary kiln is maintained under a nitrogen atmosphere.

5. The method according to any one of claims 1 to 4, wherein the rotary kiln is operated at substantially atmospheric pressure or at a slight negative pressure of 0.9 bar or more, for example 0.95 bar or more, in absolute pressure.

6. The method according to any one of claims 1 to 5, wherein each zone of the rotary kiln is operated at a temperature of 310 °C to 720 °C, preferably 400 °C to 650 °C.

7. The method according to any one of claims 1 to 6, wherein the final zone of the plurality of zones is heated to a higher temperature than the other heating zones, preferably the plurality of heating zones comprising sequential zones operated at 310 °C to 600 °C in one or two or more zones and the subsequent final zone is operated at 480 °C to 700 °C.

8. The method according to any one of claims 1 to 7, wherein the polymer feed comprises at least 85% by weight of a polyolefin polymer, preferably at least 90% by weight of a polyolefin polymer, more preferably at least 95% by weight of a polyolefin polymer, for example at least 99% by weight of a polyolefin polymer.

9. The method according to any one of claims 1 to 8, wherein the polyolefin polymer comprises or consists essentially of polyethylene and polypropylene, for example, the polyolefin polymer comprises at least 90% by weight of polyethylene and polypropylene, preferably at least 95% by weight of polyethylene and polypropylene, for example at least 99% by weight of polyethylene and polypropylene.

10. The method according to any one of claims 1 to 9, wherein the polymer feed is melted in a melt extruder.

11. The method according to claim 10, wherein the melt extruder is heated to a temperature of 250 °C to 350 °C, preferably 265 °C to 325 °C.

12. The method according to any one of claims 1 to 11, wherein calcium oxide is added to the polymer feed, preferably in an amount of up to 3% by weight.

13. The method according to any one of claims 1 to 12, wherein at least a portion of the non-condensable gas fraction is reused for heating the rotary kiln and / or for melting the polymer feed.

14. The method according to any one of claims 1 to 13, wherein the solid char product accounts for 15% by weight or less, preferably 10% by weight or less of the effluent from the kiln.

15. The method according to any one of claims 1 to 14, wherein the hydrogenation reactor in step (v) comprises a fixed bed reactor, preferably a trickle bed reactor.

16. The method according to any one of claims 1 to 15, wherein the solid char product is separated from the fluid product stream at least in part by decanter centrifugation or tricanter centrifugation.

17. The fluid product stream comprises a non-condensable gas fraction and a liquid fraction containing hydrocarbons, and the non-condensable gas fraction is separated from the liquid fraction prior to step (v), the method according to any one of claims 1 to 16. ５＋ The method according to any one of claims 1 to 16, wherein the fluid product stream comprises a non-condensable gas fraction and a liquid fraction containing hydrocarbons, and the non-condensable gas fraction is separated from the liquid fraction prior to step (v).

18. The hydrogenation catalyst is a metal catalyst, preferably the metal hydrogenation catalyst comprises a metal selected from Group VIII of the periodic table, preferably the catalyst comprises a catalyst containing Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and / or Pt, for example, a catalyst containing Ni, Co, Mo, W, Cu, Pd, Ru, Pt, preferably the catalyst is selected from CoMo, NiMo or Ni, more preferably the catalyst is NiMo; and / or the catalyst is preferably supported on a support selected from bauxite, alumina, silica, silica-alumina or zeolite, preferably alumina, according to any one of claims 1 to 17.

19. C ２０＋ The method according to any one of claims 1 to 18, wherein the wax fraction is fractionated in step (vii) to provide three separate wax fractions each having a freezing point in the range of 30 to 40 °C, 50 to 60 °C and 70 to 80 °C.

20. An apparatus for producing a wax having a melting point of less than 100°C from a polymer feed, (i) means for melting a polymer feed comprising at least 80 wt% of a polyolefin polymer to prepare a molten polymer feed, (ii) a rotary kiln reactor configured to receive the molten polymer feed from part (i), configured to provide a plurality of sequential heating zones, each zone of the rotary kiln being operated at a temperature of 300°C to 800°C to pyrolyze the molten polymer feed to produce a fluid product stream and a solid char product, said rotary kiln reactor, (iii) means for separating the solid char product from the fluid product stream, and (iv) C from part (iii) ５＋ A hydrogenation reactor configured to receive a liquid fraction of the fluid product stream containing hydrocarbons and hydrogenate the liquid fraction to produce a hydrogenated hydrocarbon product stream (v) fractionating the hydrogenated hydrocarbon product stream to produce a C wax fraction having a melting point of less than 100 °C ２０＋ means for producing a wax fraction (vi) said C from (v) ２０＋ Means for fractionating the wax fraction to produce two or more separate wax fractions each having a melting point of less than 100 °C said apparatus comprising.

21. The apparatus according to claim 20, wherein the means for fractionating the hydrogenated hydrocarbon product stream comprises a fractionation column configured to receive the hydrocarbon product stream from the hydrogenation reactor.

22. The apparatus according to claim 20 or 21, wherein the rotary kiln is configured to provide four or five or more sequential heating zones, and preferably the rotary kiln is configured to operate as described in any of claims 4 to 7.

23. The apparatus according to any of claims 20 to 22, wherein the means for melting the polymer feed comprises a melt extruder, and preferably the polymer feed is heated at a temperature of 250°C to 350°C, preferably 265°C to 325°C.

24. The apparatus according to any of claims 20 to 23, configured to reuse the gas fraction of the hydrogenated product stream for heating the rotary kiln and / or melting the polymer feed.

25. The apparatus according to any of claims 20 to 24, wherein the hydrogenation reactor in part (iv) comprises a trickle bed reactor, and preferably the catalyst is as described in claim 18.

26. The apparatus according to any of claims 20 to 25, wherein the means for separating the solid char product from the fluid product stream comprises decanter centrifugation or tricanter centrifugation for receiving the fluid product stream from the rotary kiln, and / or a char discharge port from the rotary kiln, and separately from the char discharge port, an evaporate discharge port from the rotary kiln.

27. In part (vi), C ２０＋ The device according to any one of claims 20 to 26, comprising one or more thin film evaporators configured to provide three separate wax fractions, each having a freezing point in the range of 30 to 40 °C, 50 to 60 °C, and 70 to 80 °C, for fractionating the wax fraction.

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