Recovery and conversion reaction system for mixed waste plastics

Abstract

The invention discloses a mixed waste plastic recovery and conversion reaction system which comprises a waste plastic raw material bin, a spiral feeder, a reaction furnace, a combustion chamber, a condensing device and an oil storage tank. The reaction furnace is sequentially provided with a feeding end, a reaction area and a discharging end, the reaction area comprises a plurality of reaction sections which are connected in series, the reaction sections are sequentially and continuously arranged along the length of a furnace body, and each reaction section is provided with a temperature control device which is independently opened and closed; the discharging end is communicated with a condensing device, and the condensing device is provided with a condensed kerosene outlet and a non-condensed pyrolysis gas outlet; the non-condensing pyrolysis gas outlet is divided into two paths, one path is communicated with the reaction furnace, and the other path is communicated with the combustion chamber. According to the invention, multiple reaction sections are combined and connected in series, multiple reaction mode combinations are provided, and high-value aviation kerosene can be produced. According to the invention, dechlorination can be effectively carried out before pyrolysis, and equipment corrosion, catalyst poisoning, secondary pollution and the like are prevented; according to the invention, the non-condensed gas is recovered for hydrogenation upgrading of products and self-heating of the system, so that energy is saved.

Description

Technical Field

[0001] This invention relates to the fields of environmental protection and energy chemical technology, and in particular to a reaction system that can be used to recycle mixed waste plastics and convert them into high-value oil products. Background Technology

[0002] The global plastics industry has developed rapidly, with consumption reaching 460 million tons in 2019, of which more than 75% became plastic waste, causing serious "white pollution".

[0003] Landfilling, incineration, and physical recycling are currently the mainstream methods for disposing of waste plastics. However, the former two result in high levels of secondary pollution and carbon emissions, while physical recycling is costly, and my country's waste plastic recycling rate is only 30-35%. Furthermore, since plastics are primarily made from fossil fuels, if waste plastics cannot be effectively recycled, the plastics industry's carbon emissions are projected to account for 15% of global emissions by 2050. The clean disposal and low-carbon recycling of waste plastics has become a global challenge.

[0004] Waste plastics have a high hydrocarbon content (>85%) and are widely available. They also have high volatile matter and low ash content, making pyrolysis an ideal high-value-added method for converting waste plastics into commercially viable liquid fuels. Pyrolysis offers advantages such as low pretreatment requirements, high efficiency, low cost, and low emissions. It can convert waste plastics that are difficult to physically recycle into high-value-added hydrocarbon products under high-temperature, anaerobic conditions, achieving highly efficient chemical recycling.

[0005] PVC in mixed waste plastics results in high chlorine content in the raw materials (up to 5%), which easily causes equipment corrosion and reduces product quality. Therefore, it is necessary to develop efficient dechlorination methods at the source. Furthermore, the raw material composition is complex, and the pyrolysis of polymers is mainly characterized by random breakage, leading to a wide distribution of carbon chain lengths in the products (up to C1-C60), and the presence of heavy, difficult-to-decompose products, which significantly deviates from the requirements of fuel composition. The distribution of pyrolysis products is influenced by a combination of factors, such as the raw material composition affecting the initial breakage products, the pyrolysis temperature affecting the reactivity, and the different dechlorination temperatures for PVC, suitable pyrolysis temperatures for plastics, and optimal catalyst activity temperatures. How to balance the different reaction conditions, achieve efficient dechlorination at the source, shorten the long carbon chains in complex products, and improve the yield of effective components in plastic pyrolysis fuel is a key challenge to be solved.

[0006] Aviation kerosene is composed of C8-C16 hydrocarbons of different fractions, mainly alkanes and a small amount of aromatics. As a strategic resource, global demand for aviation kerosene has been increasing year by year, reaching 360 million tons in 2018. my country is the world's second largest consumer, and demand is expected to increase to 40 million tons by 2025. The global crude oil consumption of the aviation kerosene industry is as high as 6%, comparable to the crude oil consumption of the plastics production industry. Compared with potential aviation kerosene feedstocks such as biomass, plastics have low oxygen content, high hydrogen content, and a carbon-to-hydrogen ratio highly compatible with aviation kerosene. Therefore, they have lower requirements for high-energy-consuming processes such as pressurized hydrodeoxygenation and can be converted at atmospheric pressure, making them an ideal feedstock for aviation kerosene. In recent years, the route of producing aviation kerosene through the pyrolysis of waste plastics has been considered a potentially transformative technology to promote a circular economy for plastics. Summary of the Invention

[0007] This invention provides a reaction system and apparatus for the pyrolysis and recycling of waste plastics into high-value petroleum products such as aviation kerosene. The reaction system can be configured as a multi-stage system, enabling a continuous three-stage reaction of dechlorination, pyrolysis, and catalysis. The system of this invention can solve problems such as catalytic system deactivation, inconsistent product quality, and equipment corrosion caused by fluctuations in raw material composition, improving the system's adaptability and flexibility to raw materials, and better realizing the transformation of waste plastics into high-value aviation kerosene.

[0008] This invention is achieved through the following technical solution: A mixed waste plastic recycling and conversion reaction system, the system comprising a waste plastic raw material silo, a screw feeder, a reactor, a combustion chamber, a condensation device, and an oil storage tank; One end of the screw feeder is inserted into the reactor, and the other end is located outside the reactor; the screw feeder can be connected to a motor, and the rotation speed of the screw feeder, that is, the feeding speed, is controlled by the motor; The reactor is sequentially equipped with a feed end, a reaction zone, and a discharge end, with the waste plastic raw material silo connected to the feed end. The reaction zone includes multiple reaction sections connected in series, which are arranged sequentially along the length of the furnace body. Each reaction section is equipped with an independent temperature control device. The discharge end is connected to a condensation device, which is provided with a condensed kerosene outlet and a non-condensed pyrolysis gas outlet; the condensed kerosene outlet is connected to an oil storage tank. The non-condensable pyrolysis gas outlet is divided into two paths, one of which connects to the reactor and the other to the combustion chamber.

[0009] Furthermore, the screw feeder achieves continuous feeding by rotating about a rotation axis extending in the axial direction.

[0010] The connection between the screw feeder and the reactor is sealed to ensure that the inert atmosphere inside the system is not disrupted during the feeding process.

[0011] The reactor has an inert gas inlet at the feed end, and the inert gas inlet is connected to an inert gas pipeline. The inert gas inlet is used to provide an inert atmosphere, creating an oxygen-free environment in the reactor and purging the pyrolysis volatile components throughout the reaction system; generally, the inert gas inlet is located at the very front of the reactor.

[0012] The waste plastic raw material silo is used to add waste plastic raw materials into the reactor. The waste plastic raw material silo is equipped with a sealable opening for initial loading or batch feeding.

[0013] Each of the multiple reaction sections in the reaction zone is equipped with an independent temperature control device to independently control the temperature of each reaction section.

[0014] Each reaction section may or may not be loaded with a catalyst independently.

[0015] In a preferred embodiment, the reaction zone comprises three reaction sections connected in series along the length of the furnace body: a first reaction section, a second reaction section, and a third reaction section. Each reaction section is equipped with an independently switchable temperature control device: a first temperature control device, a second temperature control device, and a third temperature control device. The first, second, and third temperature control devices are independently switched on and off and control the temperature.

[0016] In a preferred embodiment, the first temperature control device, the second temperature control device, and the third temperature control device are all electric heating furnaces used to provide a heat source and maintain the temperature. The electric heating furnaces can control the temperature of each segment separately.

[0017] The temperatures of the first, second, and third reaction stages can be controlled independently, and they can be the same or different. Alternatively, the temperature control switch can be turned off, shutting down any one of the reaction stages.

[0018] The first reaction section, the second reaction section, and the third reaction section may each be loaded with a catalyst independently or without a catalyst.

[0019] Generally, the types of reactions carried out in a reactor include at least pretreatment, high-temperature pyrolysis, and catalytic pyrolysis. Pretreatment includes desulfurization and / or dechlorination.

[0020] The first, second, and third reaction sections can each be independently classified as a pretreatment section, a high-temperature pyrolysis section, and a catalytic pyrolysis section, respectively. The temperature control device can also be turned off in any of the first, second, or third reaction sections, meaning that particular reaction section will not be activated.

[0021] The three reaction sections—pretreatment section, high-temperature pyrolysis section, and catalytic pyrolysis section—can be combined and connected in series to form different reaction modes.

[0022] The reaction mode is determined by a combination of the physical properties of the reactants, the activation temperature of the catalyst, and the target product. Different reactants, catalysts, and target products will require different reaction modes. For the recycling and degradation of waste plastics, there are multiple reaction modes available. The seven commonly used reaction modes are as follows: (a) High-temperature pyrolysis section - catalytic pyrolysis section; (ii) Pretreatment section - catalytic pyrolysis section; (III) Catalytic pyrolysis section - Catalytic pyrolysis section; (iv) Pretreatment section - high-temperature pyrolysis section - catalytic pyrolysis section; (v) High-temperature pyrolysis section - catalytic pyrolysis section - catalytic pyrolysis section; (vi) Pretreatment section - catalytic pyrolysis section - catalytic pyrolysis section; (vii) Catalytic pyrolysis section - catalytic pyrolysis section - catalytic pyrolysis section.

[0023] Reaction modes (I), (II), and (III) have only two reaction sections. For a reactor with three reaction sections, simply turn off the temperature control device of any one reaction section.

[0024] In the furnace body of the reaction section of the catalytic pyrolysis section, a catalyst needs to be loaded. A fixed catalyst bed can be used to load the catalyst.

[0025] In reaction modes (iii), (v), (vi), and (vii), there are two or three catalytic pyrolysis sections, indicating that the catalysts or reaction temperatures of the two reaction sections are different, and different catalytic pyrolysis reactions are carried out respectively.

[0026] For reactants such as pure polyethylene and polypropylene, which contain only carbon and hydrogen elements and do not require pretreatment, reaction mode (I) can be selected, which adopts a two-stage system of high-temperature pyrolysis section and catalytic pyrolysis section.

[0027] For the use of acidic and alkaline catalysts in series, a three-stage system of reaction mode (VI) – pretreatment section – catalytic pyrolysis section – catalytic pyrolysis section can be selected.

[0028] When the target product is fuel gas, the reaction mode (V) can be selected as a three-stage system of high temperature pyrolysis section - catalytic pyrolysis section - catalytic pyrolysis section.

[0029] For reaction raw materials containing PVC, a three-stage reaction system consisting of reaction mode (IV) pretreatment section - high temperature pyrolysis section - catalytic pyrolysis section can be selected.

[0030] Furthermore, for a reactor containing a catalytic pyrolysis section, the front end of the furnace body of the catalytic pyrolysis section is provided with a non-condensable pyrolysis gas recovery port; the non-condensable pyrolysis gas outlet is divided into two paths, one path connecting to the non-condensable pyrolysis gas recovery port of the reactor, and the other path connecting to the combustion chamber; the combustion chamber is provided with an air inlet, a circulating combustion inlet, and a combustion gas outlet; the non-condensable pyrolysis gas recovery port is connected to the circulating combustion inlet.

[0031] A valve can be installed at the outlet of the non-condensable pyrolysis gas to control and regulate the flow rate of the non-condensable pyrolysis gas connecting the combustion chamber and the reactor.

[0032] Furthermore, the reaction system is equipped with a heat exchange system, and the combustion gas outlet of the combustion chamber is connected to the heat exchange system. The heat exchange system is located outside the reaction zone and surrounds the entire reaction zone, providing circulated and recovered heat for multiple reaction sections.

[0033] Furthermore, the heat exchange system is equipped with a gas pipeline and a heat exchange medium pipeline. Combustion gas is introduced into the gas pipeline of the heat exchange system, and the heat exchange medium is provided in the heat exchange medium pipeline. The combustion gas and the heat exchange medium exchange heat. The heat exchange medium pipeline surrounds the reaction zone and provides heat to multiple reaction sections of the reaction zone.

[0034] Furthermore, the heat exchange system is equipped with a cooling combustion gas outlet, which can be directly discharged or connected to a tail gas absorption device before being discharged.

[0035] In this invention, the combustion chamber is used to process non-condensable combustible gases and provide heat. After pyrolysis catalysis, most of the oil and gas can be condensed into liquid oil, but some non-condensable combustible gases will always be produced. After the non-condensable pyrolysis gas is introduced into the combustion chamber, it mixes with air to obtain a mixed gas. The combustion chamber ignites the mixed gas, and the heat generated by combustion can be used to heat the reactor, achieving energy self-sufficiency of the system and reducing external fuel consumption.

[0036] Another non-condensable pyrolysis gas can be reintroduced into the reactor. The non-condensable pyrolysis gas enters the catalytic pyrolysis section, which contains a large amount of hydrogen. This hydrogenation can enhance the pyrolysis gas in the catalytic pyrolysis section and increase the saturation of the product oil.

[0037] Furthermore, for reaction modes that include a pretreatment section and the pretreatment section is a dechlorination pretreatment section, preferably, a chlorine-containing gas outlet is provided at the tail end of the furnace body of the dechlorination pretreatment section, and a dechlorination gas inlet is provided at the front end of the furnace body of the dechlorination pretreatment section.

[0038] The terms "front end" and "tail end" are defined based on the direction of raw material feeding and the direction of gas flow: the feeding end and the gas inflow end are the front end, and the discharging end and the gas outflow end are the tail end.

[0039] When the reaction system of the present invention processes chlorine-containing waste plastics, it also includes an absorption tower. The absorption tower is provided with a chlorine-containing gas inlet and a dechlorination gas outlet. The chlorine-containing gas outlet of the reactor is connected to the chlorine-containing gas inlet of the absorption tower, and the dechlorination gas outlet is connected to the dechlorination gas inlet of the reactor.

[0040] Furthermore, a gas extraction pump is installed on the pipeline at the dechlorination gas outlet to extract the chlorine-containing gas generated in the dechlorination pretreatment section into the absorption tower.

[0041] The absorption tower is used to purify the chlorine-containing gas generated in the dechlorination pretreatment section and remove acidic impurities. The chlorine-containing gas product exiting the reactor contains acidic gases such as hydrogen chloride. The absorption tower is typically filled with an alkaline solution or a solid adsorbent (alkali metal / natural ore, etc.). The chlorine-containing gas enters from the bottom of the tower and comes into countercurrent contact with the absorbent flowing from top to bottom. The acidic gases are chemically absorbed, resulting in pure hydrocarbon gas, protecting downstream equipment and ensuring product purity. The dechlorinated gas re-enters the reactor to continue the reaction.

[0042] In a preferred embodiment, reaction mode (four) is employed to recycle chlorinated mixed waste plastics. The first reaction section is a dechlorination pretreatment section, the second reaction section is a high-temperature pyrolysis section, and the third reaction section is a catalytic pyrolysis section. The catalytic pyrolysis section is equipped with a fixed catalyst bed for loading the catalyst. The catalyst is generally a transition metal oxide-supported modified heterogeneous solid acid catalyst used for catalytic conditioning of the pyrolysis gas components. Under the action of the catalyst, the pyrolysis gas undergoes a series of catalytic reactions such as cracking, isomerization, and aromatization, thereby generating products of higher quality and closer to the composition of aviation kerosene. The catalyst is generally loaded in the order of quartz wool-catalyst-quartz wool.

[0043] Furthermore, the reaction system of the present invention is also equipped with a residue collection device. The furnace body of the reactor of the present invention is provided with a residue outlet, which is connected to the residue collection device. The residue collection device is used to periodically collect the solid residue generated by the reaction, so as to facilitate centralized treatment and keep the inside of the reactor clean.

[0044] Generally, the residue outlet can be located at the front end of the furnace body in the last catalytic pyrolysis section.

[0045] In a preferred embodiment, such as the reaction mode (four) reaction system, the furnace body between the high-temperature pyrolysis section and the catalytic pyrolysis section is provided with a residue outlet.

[0046] In a preferred embodiment, the residue collection device is an ash hopper or an openable container.

[0047] This invention also provides a method for preparing aviation kerosene from mixed waste plastics through dechlorination-pyrolysis-catalysis, the method utilizing a reaction system of reaction mode (four), the method comprising the following steps: (1) Place the waste plastic in the waste plastic raw material silo, and fill the solid acid catalyst in the catalyst fixed bed in the order of quartz wool-catalyst-quartz wool. Turn on the first temperature control device, the second temperature control device, and the third temperature control device so that the temperatures of the dechlorination pretreatment section, the high temperature pyrolysis section, and the catalytic pyrolysis section are 200-360℃, 450-600℃, and 500-650℃, respectively. (2) Open the inert gas inlet and the vacuum pump. Inert gas is introduced into the inert gas inlet to purge the entire reaction system and exhaust the air, so that the reactor is an oxygen-free environment. The waste plastic raw materials in the waste plastic raw material silo are fed into the reactor through the screw feeder. The dechlorination reaction is carried out in the dechlorination pretreatment section. The generated chlorine-containing gas enters the absorption tower. The dechlorinated gas returns to the reactor to participate in the subsequent reaction. (3) The dechlorinated waste plastic is fed into the high-temperature pyrolysis section by a screw feeder, where a high-temperature pyrolysis reaction occurs, generating pyrolysis oil and gas, a small amount of coke, and residue. The pyrolysis oil and gas are carried by the carrier gas into the catalytic pyrolysis section for catalytic pyrolysis. The generated products enter the condensation device and are cooled and liquefied. The liquid fuel products flow into the oil storage tank for collection. The non-condensable pyrolysis gas is discharged from the condensation device and divided into two paths. One path enters the combustion chamber and mixes with air, where it is fully combusted. The generated high-temperature combustion gas is fed into the heat exchange system to provide heat for the entire reaction zone. The other path of non-condensable pyrolysis gas returns to the reactor and enters the catalytic pyrolysis section for hydrogenation enhancement. The solid residue generated during the entire reaction process is collected by the residue collection device and cleaned periodically.

[0048] The reaction system of this invention has three reaction sections connected in series, used for dechlorination, pyrolysis, and catalytic conditioning of waste plastics, respectively. This system can be used for the pyrolysis and catalytic pyrolysis of complex organic solid wastes such as waste plastics, recovering and producing high-value petroleum products such as aviation kerosene and diesel.

[0049] This invention comprises three reaction sections, each powered by an electric furnace providing heat and insulation. The furnaces can independently control the temperature of each section. The first section of the reaction system is a dechlorination pretreatment section, where the mixed waste plastics undergo primary decomposition. Chlorine in the chlorinated plastics is released as HCl gas, thus undergoing dechlorination. The chlorinated gas is then introduced into an absorption tower and absorbed by a low-temperature coupled alkali metal / natural ore absorbent, achieving low-temperature removal of chlorine at its source. The pretreated and dechlorinated mixed waste plastics are then introduced into the second reaction section of the reaction zone via a spiral sampler. The second reaction section is a high-temperature pyrolysis section, where the pretreated and dechlorinated mixed waste plastics undergo preliminary pyrolysis, converting the plastic macromolecules into medium- and long-chain hydrocarbons, i.e., pyrolysis gas. Subsequently, the pyrolysis gas carrier gas flows into the third reaction section of the reaction system. In the furnace of the third reaction section, a transition metal oxide-supported modified multiphase solid acid catalyst is packed in the order of quartz wool-catalyst-quartz wool for catalytic conditioning of the pyrolysis gas.

[0050] A further improvement of this invention is that the reaction system integrates a circulating hydrogen supply and heating system, so that the non-condensable pyrolysis gas produced at the end of the reaction re-enters the three-stage reaction system. Part of it enters the third reaction stage for hydrogenation enhancement to increase the saturation of the product oil, and the other part enters the combustion chamber to mix and burn with air. The flue gas after combustion heats the reaction system.

[0051] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. This invention innovatively employs a multi-stage reaction section combination series design, providing up to seven different reaction mode combinations. The optimal reaction mode can be flexibly configured according to different waste plastic raw material components, catalyst characteristics, and target product requirements, realizing multiple uses for a single device, greatly improving equipment utilization and experimental efficiency, and enhancing raw material adaptability and operational flexibility.

[0052] 2. The three-stage reaction system of this invention is equipped with an independent pretreatment dechlorination stage, which effectively removes harmful impurities such as chlorine before pyrolysis. This fundamentally solves the problems of corrosion, catalyst poisoning and secondary pollution generated during the pyrolysis of waste plastics, and significantly improves the purity and quality of the final aviation kerosene components.

[0053] 3. This invention integrates three key functions—pretreatment, pyrolysis, and catalysis—into a single unit, achieving continuous and integrated processing of the entire process for converting mixed waste plastics. This overcomes the industry's technical bottlenecks caused by traditional single-mode pyrolysis or fixed-mode catalytic conversion, which struggle to handle complex raw materials and unstable product quality. Through mode switching and a recycling system, this invention achieves efficient, flexible, and high-value conversion of complex mixed waste plastics, significantly improving the selectivity and yield of aviation kerosene components.

[0054] 4. This invention offers high flexibility, enabling separate temperature control in three stages, allowing different reactions to proceed under optimal conditions and improving reaction efficiency.

[0055] 5. Through the innovative design of the circulating gas supply and heating system, this invention uses non-condensable gas for both in-situ hydrogenation and quality improvement of the product and system self-heating. This improves product quality while achieving energy recycling and enables the graded, directional, and efficient recovery and reuse of non-condensable gases from the reaction. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the device structure of a reaction system for recycling and converting mixed waste plastics according to the present invention.

[0057] Explanation of reference numerals in the attached diagram: 1. Inert gas inlet; 2. Waste plastic raw material silo; 3. Screw feeder; 4. Air pump; 5. Dechlorination gas inlet; 6. Absorption tower; 61. Chlorine-containing gas inlet; 62. Dechlorination gas outlet; 7. Chlorine-containing gas outlet; 8. Air inlet; 9. Combustion chamber; 10. Circulating combustion inlet; 11. Non-condensable pyrolysis gas recovery inlet; 12. Combustion gas outlet; 13. Non-condensable pyrolysis gas outlet; 14. Catalyst fixed bed; 15. Reactor; 151. Feed end; 152. Reaction zone; 1521. First reaction section; 1522. Second reaction section; 1523. Third reaction section; 153. Discharge end; 16. First temperature control device; 17. Second temperature control device; 18. Third temperature control device; 19. Residue collection device; 20. Condensation device; 21. Oil storage tank; 22. Heat exchange system. Detailed Implementation

[0058] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited thereto.

[0059] Example 1, such as Figure 1 As shown, the present invention provides a reaction system for recycling and converting mixed waste plastics. The system includes a waste plastic raw material silo 2, a screw feeder 3, a reactor 15, a combustion chamber 9, a condensation device 20, and an oil storage tank 21. One end of the screw feeder 3 is inserted into the reactor 15, and the other end is located outside the reactor 15. The part of the screw feeder 3 inside the reactor is a screw propulsion rod. The screw propulsion rod is provided with a screw shaft and a rotation axis extending in the axial direction, and continuous feeding is achieved by rotation.

[0060] The part of the screw feeder 3 outside the reactor 15 can be connected to a motor. The rotation speed of the screw feeder can be controlled by the motor, thereby regulating the propulsion speed of the raw materials in the reactor, that is, controlling the reaction time of the raw materials in each stage.

[0061] The connection between the screw feeder 3 and the reactor 15 forms a seal, ensuring that the inert atmosphere inside the system is not disrupted during the feeding process. The screw feeder 3 stably, uniformly, and controllably conveys waste plastic particles from the hopper to the reactor 15 without compromising the internal airtightness and oxygen-free environment of the reactor 15, thus solving the problems of low batch feeding efficiency and unstable gas pressure.

[0062] The reactor 15 is provided with a feed end 151, a reaction zone 152 and a discharge end 153 in sequence. The waste plastic raw material bin 2 is connected to the feed end 151. The waste plastic raw material bin 2 is used to add waste plastic raw materials into the reactor 15. The waste plastic raw material bin 2 is provided with a sealable opening for initial loading or batch feeding.

[0063] The front end of the reactor is also provided with an inert gas inlet 1, which is connected to an inert gas pipeline; the inert gas inlet 1 is used to provide an inert atmosphere to create an oxygen-free environment in the reactor 15 and to purge the pyrolysis gas to the entire reaction system.

[0064] The reaction zone 152 includes multiple reaction sections connected in series. The reaction sections are arranged sequentially along the length of the furnace body. Each reaction section is equipped with an independent temperature control device to control the temperature of the reaction section.

[0065] Each reaction section may or may not be loaded with a catalyst independently.

[0066] In a preferred embodiment, such as Figure 1 As shown, the reaction zone is continuously arranged in series along the length of the furnace body, consisting of three reaction sections: the first reaction section 1521, the second reaction section 1522, and the third reaction section 1523. Each reaction section is equipped with an independently switchable temperature control device: the first temperature control device 16, the second temperature control device 17, and the third temperature control device 18. The first temperature control device 16, the second temperature control device 17, and the third temperature control device 18 are independently switched on and off and control the temperature.

[0067] Furthermore, the first temperature control device 16, the second temperature control device 17, and the third temperature control device 18 can be electric heating furnaces to provide heat sources and insulation for the reaction furnaces. The electric heating furnaces can control the temperature of each section separately, thereby realizing the control of different reaction zones.

[0068] The temperatures of the first reaction section 1521, the second reaction section 1522, and the third reaction section 1523 can be controlled independently, and they can be the same or different. Alternatively, the temperature control device can be turned off, shutting down any one of the reaction sections.

[0069] The first reaction section 1521, the second reaction section 1522, and the third reaction section 1523 may each be loaded with or not loaded with catalysts.

[0070] The reactions carried out in the reactor include at least pretreatment, pyrolysis, and catalytic pyrolysis. The first reaction section 1521, the second reaction section 1522, and the third reaction section 1523 can each be independently designated as a pretreatment section, a pyrolysis reaction section, and a catalytic pyrolysis section, respectively. The temperature control device for the first reaction section 1521, the second reaction section 1522, and the third reaction section 1523 can also be turned off, meaning that this reaction section is not activated.

[0071] The pretreatment section can perform dechlorination and / or desulfurization reactions. For chlorinated plastics such as PVC, dechlorination pretreatment is required, and for sulfur-containing plastics, desulfurization pretreatment is required. Pretreatment can remove chlorine and sulfur elements from waste plastics, preventing corrosion of equipment and impact on product quality during subsequent high-temperature reactions.

[0072] For chlorinated plastics such as PVC, under an inert gas atmosphere and heated to a relatively low temperature (200~360℃), the chlorinated plastics undergo a primary decomposition reaction. This reaction is mainly a dechlorination process, in which the chlorine in the chlorinated plastic is released in the form of HCl gas, thus undergoing dechlorination.

[0073] The pyrolysis reaction section carries out the pyrolysis reaction. The pyrolysis reaction takes place at high temperature, where the large molecular chains in the waste plastic break down into smaller molecules, transforming into a mixture of pyrolysis oil and gas, a small amount of coke, and residue.

[0074] The temperature of the pyrolysis reaction depends on the type of plastic and the desired product to be recycled. Generally, at temperatures above 600℃, the main pyrolysis product is a mixture of fuel gases, such as methane and ethylene, which are light hydrocarbons. At temperatures between 400 and 600℃, the pyrolysis products include a mixture of light hydrocarbons, naphtha, heavy oil, kerosene, and waxy solids. For specific plastic types, the pyrolysis products of PE and PP are mainly fuel gases and fuel oils, while the pyrolysis product of PS is mainly styrene monomer; and the pyrolysis products of PVC are mainly light hydrocarbons, aromatic hydrocarbons, tar, and coke.

[0075] The catalytic pyrolysis section carries out catalytic pyrolysis reactions. Catalytic pyrolysis involves adding a catalyst during the pyrolysis reaction to cause characteristic reactions such as hydrogen transfer and condensation in the pyrolysis products, as well as isomerization and aromatization, to obtain products with relative molecular mass and structure within a certain range, thereby improving the quality of oil products.

[0076] Catalytic pyrolysis can be used directly on waste plastics, or the pyrolysis gas from waste plastics can be further catalytically converted.

[0077] The temperature of catalytic pyrolysis is generally 450~650℃, which can be adjusted according to the reaction raw materials and target products.

[0078] Catalysts used in catalytic pyrolysis include solid acid catalysts, which can donate protons during the reaction, causing a transfer process to accompany the reaction, thereby carrying out the isomerization reaction.

[0079] The pretreatment section, pyrolysis reaction section, and catalytic pyrolysis section are combined and connected in series to form different reaction modes. The furnace body of the catalytic pyrolysis section needs to be filled with catalyst. A catalyst fixed bed 14 can be used to load the catalyst.

[0080] There are multiple reaction modes for the recycling and degradation of waste plastics. The seven most commonly used reaction modes are as follows: (a) Pyrolysis reaction section - catalytic pyrolysis section; (ii) Pretreatment section - catalytic pyrolysis section; (III) Catalytic pyrolysis section - Catalytic pyrolysis section; (iv) Pretreatment section - High-temperature pyrolysis section - Catalytic pyrolysis section (v) Pyrolysis reaction section - catalytic pyrolysis section - catalytic pyrolysis section; (vi) Pretreatment section - catalytic pyrolysis section - catalytic pyrolysis section; (vii) Catalytic pyrolysis section - catalytic pyrolysis section - catalytic pyrolysis section.

[0081] Reaction modes (I), (II), and (III) have only two reaction sections. For a reactor with three reaction sections, simply turn off the temperature control device of any one reaction section.

[0082] In reaction modes (iii), (v), (vi), and (vii), there are two or three catalytic pyrolysis sections, indicating that the catalysts or reaction temperatures of the two or three reaction sections are different, and different catalytic pyrolysis reactions are carried out.

[0083] The length of the screw propeller depends on the feeding and reaction methods. Generally, the screw propeller is inserted into the pretreatment section and the high-temperature pyrolysis section, but not into the catalytic pyrolysis section.

[0084] Waste plastics contain only polyethylene and polypropylene, which are only carbon and hydrogen elements and do not require pretreatment. Therefore, reaction mode (I) can be selected, which adopts a two-stage system of pyrolysis reaction section and catalytic pyrolysis section.

[0085] For the use of acidic and alkaline catalysts in series, a three-stage system of reaction mode (VI) – pretreatment section – catalytic pyrolysis section – catalytic pyrolysis section can be selected.

[0086] When the target product is fuel gas, the reaction mode (V) can be selected as a three-stage system of pyrolysis reaction section - catalytic pyrolysis section - catalytic pyrolysis section.

[0087] When waste plastic raw materials contain chlorinated plastics such as PVC, a three-stage reaction system consisting of reaction mode (IV) – pretreatment section – pyrolysis reaction section – catalytic pyrolysis section can be selected.

[0088] In a preferred embodiment, the reaction system of this example is used to process chlorinated plastics through dechlorination-pyrolysis-catalytic production of aviation kerosene. The first reaction section 1521 is a dechlorination pretreatment section, the second reaction section 1522 is a pyrolysis reaction section, and the third reaction section 1523 is a catalytic pyrolysis section. The catalytic pyrolysis section is equipped with a catalyst fixed bed 14 for loading the catalyst. The catalyst is generally a transition metal oxide supported modified heterogeneous solid acid catalyst used for conditioning the pyrolysis gas components. The catalyst is generally loaded in the order of quartz wool-catalyst-quartz wool. In this embodiment, the screw propeller is inserted into the low-temperature dechlorination section and the high-temperature pyrolysis section, but does not enter the catalytic pyrolysis section.

[0089] In a preferred embodiment, the temperature of the low-temperature dechlorination section is controlled at 200~360℃, the temperature of the high-temperature pyrolysis section is controlled at 450~600℃, and the temperature of the catalytic pyrolysis section is controlled at 500~650℃.

[0090] In the low-temperature dechlorination section, the chlorine in the waste plastics (mainly from polyvinyl chloride) undergoes a primary decomposition reaction at a certain temperature. The chlorine in the chlorinated plastics is released as HCl gas, undergoing dechlorination. The chlorinated gas then enters the absorption tower for absorption and purification. The dechlorinated raw material enters the high-temperature pyrolysis section, where the plastic macromolecular chains break down under heat, undergoing a high-temperature pyrolysis reaction, transforming into a mixture of pyrolysis oil and gas, a small amount of coke, and residue. In the catalytic pyrolysis section, the pyrolysis oil and gas undergo a series of catalytic reactions such as cracking, isomerization, and aromatization under the action of a catalyst, thereby generating products of higher quality and closer to the composition of aviation kerosene. A small amount of coke and residue can be recovered through the residue collection device 19.

[0091] Furthermore, since the system in this embodiment includes a catalytic thermal stage and a dechlorination pretreatment section, it is preferable to have a chlorine-containing gas outlet 7 at the tail end of the furnace body of the dechlorination pretreatment section (first reaction section 1521), and a non-condensable pyrolysis gas recovery port 11 at the front end of the furnace body of the catalytic pyrolysis section (third reaction section 1523); a dechlorination gas inlet 5 is provided at the front end of the furnace body of the dechlorination pretreatment section (first reaction section 1521). An absorption tower 6 is also provided for absorbing the chlorine-containing gas.

[0092] The terms "front end" and "tail end" are defined based on the direction of raw material feeding and the direction of gas flow: the feeding end and the gas inflow end are the front end, and the discharging end and the gas outflow end are the tail end.

[0093] The discharge end 153 of the reactor 15 is connected to the condensing device 20, which is provided with a condensed kerosene outlet and a non-condensed pyrolysis gas outlet 13; the condensed kerosene outlet is connected to the oil storage tank 21. The non-condensable pyrolysis gas outlet 13 is divided into two paths: one path is connected to the non-condensable pyrolysis gas recovery port 11 of the reactor 15, and the other path is connected to the circulating combustion inlet 10 of the combustion chamber 9; the combustion chamber 9 is provided with an air inlet 8, a circulating combustion inlet 10, and a combustion gas outlet 12. A valve can be installed at the non-condensable pyrolysis gas outlet to control and regulate the flow rate between the combustion chamber and the reactor. Combustion gas outlet 12 is connected to heat exchange system 22, which is located outside the reaction zone 152 and surrounds the entire reaction zone 152, providing recycled heat for multiple reaction sections.

[0094] Furthermore, the heat exchange system is provided with a gas pipeline and a heat exchange medium pipeline. Combustion gas is introduced into the gas pipeline of the heat exchange system, and the heat exchange medium is provided in the heat exchange medium pipeline. The combustion gas and the heat exchange medium exchange heat. The heat exchange medium pipeline surrounds the reaction zone 152 and provides heat to the multiple reaction sections of the reaction zone 152.

[0095] Furthermore, the heat exchange system is equipped with a cooling combustion gas outlet, which can be directly discharged or connected to a tail gas absorption device before being discharged.

[0096] In this invention, the combustion chamber 9 is used to process non-condensable combustible gases and provide heat. After pyrolysis catalysis, most of the oil and gas can be condensed into liquid oil, but some non-condensable combustible gases, such as hydrogen and C1-C4 alkanes and alkenes, will always be generated. After the non-condensable pyrolysis gas is introduced into the combustion chamber 9, it mixes with air to obtain a mixed gas. The combustion chamber 9 ignites the mixed gas, and the heat generated by combustion can be used to heat the reactor 15, which can replace part of the external electric heating, realize the system's energy self-sufficiency, and greatly reduce energy consumption.

[0097] Another non-condensable pyrolysis gas can be reintroduced into reactor 15. Since it contains a large amount of hydrogen, it can be hydrogenated in the catalytic pyrolysis section to increase the saturation of the product oil.

[0098] The absorption tower 6 is used to absorb chlorine-containing gas. The absorption tower 6 is provided with a chlorine-containing gas inlet 61 and a dechlorinated gas outlet 62. The chlorine-containing gas outlet 7 is connected to the chlorine-containing gas inlet 61 of the absorption tower 6, and the dechlorinated gas outlet 62 is connected to the dechlorinated gas inlet 5. The chlorine-containing gas inlet 61 is generally located at the bottom of the absorption tower 6, and the dechlorinated gas outlet 62 is generally located at the top of the absorption tower 6.

[0099] A gas extraction pump 4 is installed on the pipeline of the dechlorination gas outlet 62 to extract the chlorine-containing gas generated in the dechlorination pretreatment section and enter the absorption tower 6.

[0100] The absorption tower 6 is used to purify the chlorine-containing gas generated in the dechlorination pretreatment section and remove acidic impurities. The gaseous products exiting the reactor contain acidic gases such as hydrogen chloride. The absorption tower 6 is typically filled with an alkaline solution or a solid adsorbent (alkali metal / natural ore, etc.). The chlorine-containing gas enters from the bottom of the absorption tower and comes into countercurrent contact with the absorbent flowing from top to bottom. The acidic gases are chemically absorbed or physically adsorbed, thereby obtaining pure hydrocarbon gases, preventing equipment corrosion and environmental pollution, protecting the catalyst for subsequent catalytic reactions, protecting downstream equipment, and ensuring product purity. The dechlorinated gas re-enters the reactor 15 to continue the reaction.

[0101] Furthermore, the furnace body between the high-temperature pyrolysis section (second reaction section 1522) and the catalytic pyrolysis section (third reaction section 1523) is provided with a residue outlet, which is connected to a residue collection device 19. The residue collection device 19 is used to periodically collect the solid residue generated by the reaction, so as to facilitate centralized treatment and keep the inside of the reactor 15 clean.

[0102] The residue collection device 19 can be an ash hopper or an openable container.

[0103] This invention also provides a method for efficiently producing aviation kerosene components from mixed waste plastics through dechlorination-pyrolysis-catalysis using the above-mentioned apparatus, the method comprising the following steps: (1) Place the waste plastic in the waste plastic raw material silo, and fill the solid acid catalyst in the catalyst fixed bed in the order of quartz wool-catalyst-quartz wool. Turn on the first temperature control device, the second temperature control device, and the third temperature control device so that the temperatures of the dechlorination pretreatment section, the high temperature pyrolysis section, and the catalytic pyrolysis section are 200-360℃, 450-600℃, and 500-650℃, respectively. (2) Open the inert gas inlet and the vacuum pump. Inert gas such as nitrogen is introduced into the inert gas inlet to purge the entire reaction system and exhaust the air to ensure that the reactor is a strictly oxygen-free environment. The waste plastic raw materials in the waste plastic raw material silo are fed into the reactor through the screw feeder and dechlorination reaction is carried out in the dechlorination pretreatment section. The generated chlorine-containing gas is carried by the carrier gas and enters the absorption tower through the chlorine-containing gas outlet. The dechlorinated gas returns to the reactor from the dechlorination gas inlet to participate in the subsequent reaction. (3) The dechlorinated waste plastic is fed into the high-temperature pyrolysis section by a screw feeder, where a high-temperature pyrolysis reaction occurs, generating pyrolysis oil and gas, a small amount of coke, and residue. The pyrolysis oil and gas are carried by the carrier gas into the catalytic pyrolysis section for catalytic pyrolysis. The generated products enter the condensation device and are cooled and liquefied. The liquid fuel products flow into the oil storage tank for collection. The non-condensable pyrolysis gas is discharged from the condensation device and divided into two paths. One path enters the combustion chamber and mixes with air, where it is fully combusted. The generated high-temperature combustion gas is fed into the heat exchange system to provide heat for the entire reaction zone. The other path of non-condensable pyrolysis gas returns to the reactor and enters the catalytic pyrolysis section for hydrogenation enhancement. The solid residue generated during the entire reaction process is collected by the residue collection device and cleaned periodically. This mixed waste plastics-to-aviation kerosene reaction system uses 10 kg of mixed waste plastics as raw material, including 3 kg of PVC (polyvinyl chloride), 2 kg of PE (polyethylene), and 5 kg of PP (polypropylene). The raw material is crushed, pre-treated to remove impurities, and then fed into the reaction unit. Under process conditions of 400-450℃ and 0.1-0.3 MPa, through core processes such as pyrolysis, dechlorination, hydrorefining, and fractionation, 6.8 kg of aviation kerosene and 2.6 kg of residue are ultimately produced, with an additional 0.4 kg of material volatilizing as light gases (such as methane and ethane). The components of aviation kerosene were characterized using an Agilent gas chromatograph (GC-7890B) coupled with mass spectrometry. Alkanes constituted the largest proportion at 77.3%, primarily including n-alkanes (C10-C15, such as n-decane and n-dodecane, accounting for 43.1%) and isoalkanes (C9-C16, such as 2-methylnonane and 3-ethylundecane, accounting for 34.2%). These components ensure high combustion efficiency and good low-temperature fluidity of aviation kerosene. Cycloalkanes accounted for 16.1%, mainly monocyclic cycloalkanes (such as methylcyclohexane and ethylcyclooctane), which improve fuel stability and prevent excessive carbon buildup during combustion. Aromatic products accounted for 6.6%, primarily monocyclic aromatics (such as toluene and ethylbenzene). The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A mixed waste plastic recycling and conversion reaction system, characterized in that... The system includes a waste plastic raw material silo, a screw feeder, a reactor, a combustion chamber, a condensation device, and an oil storage tank; One end of the screw feeder is inserted into the reactor, and the other end is located outside the reactor; The reactor is sequentially equipped with a feed end, a reaction zone, and a discharge end, with the waste plastic raw material silo connected to the feed end. The reaction zone includes multiple reaction sections connected in series, which are arranged sequentially along the length of the furnace body. Each reaction section is equipped with an independent temperature control device. The discharge end is connected to a condensation device, which is provided with a condensed kerosene outlet and a non-condensed pyrolysis gas outlet; the condensed kerosene outlet is connected to an oil storage tank. The non-condensable pyrolysis gas outlet is divided into two paths, one of which connects to the reactor and the other to the combustion chamber.

2. The reaction system as described in claim 1, characterized in that... The reaction zone consists of three reaction sections connected in series along the length of the furnace body: the first reaction section, the second reaction section, and the third reaction section. Each reaction section is equipped with an independently switchable temperature control device: the first temperature control device, the second temperature control device, and the third temperature control device. The first temperature control device, the second temperature control device, and the third temperature control device are independently switched on and off and control the temperature. The first reaction section, the second reaction section, and the third reaction section may or may not be loaded with catalyst.

3. The reaction system as described in claim 2, characterized in that... The first, second, and third reaction stages are each independently a pretreatment stage, a high-temperature pyrolysis stage, and a catalytic pyrolysis stage, respectively. These three reaction stages are combined and connected in series to form the following reaction mode: (a) High-temperature pyrolysis section - catalytic pyrolysis section; (ii) Pretreatment section - catalytic pyrolysis section; (III) Catalytic pyrolysis section - Catalytic pyrolysis section; (iv) Pretreatment section - high-temperature pyrolysis section - catalytic pyrolysis section; (v) High-temperature pyrolysis section - catalytic pyrolysis section - catalytic pyrolysis section; (vi) Pretreatment section - catalytic pyrolysis section - catalytic pyrolysis section; (vii) Catalytic pyrolysis section - catalytic pyrolysis section - catalytic pyrolysis section.

4. The reaction system as described in claim 3, characterized in that... When the reaction mode includes a catalytic pyrolysis section, the front end of the furnace body of the catalytic pyrolysis section is provided with a non-condensable pyrolysis gas recovery port; the non-condensable pyrolysis gas outlet is divided into two paths, one path is connected to the non-condensable pyrolysis gas recovery port of the reactor, and the other path is connected to the combustion chamber; the combustion chamber is provided with an air inlet, a circulating combustion inlet, and a combustion gas outlet; the non-condensable pyrolysis gas recovery port is connected to the circulating combustion inlet.

5. The reaction system as described in claim 4, characterized in that... The reaction system is equipped with a heat exchange system. The combustion gas outlet of the combustion chamber is connected to the heat exchange system. The heat exchange system is located outside the reaction zone and surrounds the entire reaction zone, providing heat to multiple reaction sections.

6. The reaction system as described in claim 3, characterized in that... When the reaction mode includes a pretreatment section and the pretreatment section is a dechlorination pretreatment section, a chlorine-containing gas outlet is provided at the tail end of the furnace body of the dechlorination pretreatment section, and a dechlorination gas inlet is provided at the front end of the furnace body of the dechlorination pretreatment section. The reaction system also includes an absorption tower, which has a chlorine-containing gas inlet and a dechlorination gas outlet. The chlorine-containing gas outlet of the reactor is connected to the chlorine-containing gas inlet of the absorption tower, and the dechlorination gas outlet is connected to the dechlorination gas inlet of the reactor.

7. The reaction system as described in claim 6, characterized in that... A vacuum pump is installed on the dechlorination gas outlet pipeline to extract chlorine-containing gas generated in the dechlorination pretreatment section into the absorption tower; an inert gas inlet is provided at the feed end of the reactor, and the inert gas inlet is connected to an inert gas pipeline.

8. The reaction system as described in claim 3, characterized in that... The reaction system is also equipped with a residue collection device, and the furnace body is provided with a residue outlet, which is connected to the residue collection device.

9. The reaction system as described in claim 3, characterized in that... The first reaction section of the reaction zone is a dechlorination pretreatment section, the second reaction section is a high-temperature pyrolysis section, and the third reaction section is a catalytic pyrolysis section; the catalytic pyrolysis section is equipped with a catalyst fixed bed for loading the catalyst; The reactor has an inert gas inlet at the feed end, and the inert gas inlet is connected to an inert gas pipeline. The front end of the furnace body of the catalytic pyrolysis section is provided with a non-condensable pyrolysis gas recovery port; the non-condensable pyrolysis gas outlet is divided into two paths, one path is connected to the non-condensable pyrolysis gas recovery port of the reactor, and the other path is connected to the combustion chamber; the combustion chamber is provided with an air inlet, a circulating combustion inlet, and a combustion gas outlet; the non-condensable pyrolysis gas recovery port is connected to the circulating combustion inlet. The reaction system is equipped with a heat exchange system, and the combustion gas outlet of the combustion chamber is connected to the heat exchange system. The heat exchange system is located outside the reaction zone and surrounds the entire reaction zone, providing heat for multiple reaction sections. A chlorine-containing gas outlet is provided at the tail end of the furnace body in the dechlorination pretreatment section, and a dechlorination gas inlet is provided at the front end of the furnace body in the dechlorination pretreatment section. The reaction system also includes an absorption tower, which has a chlorine-containing gas inlet and a dechlorination gas outlet. The chlorine-containing gas outlet of the reactor is connected to the chlorine-containing gas inlet of the absorption tower, and the dechlorination gas outlet is connected to the dechlorination gas inlet of the reactor. A gas extraction pump is installed on the pipeline at the dechlorination gas outlet to extract the chlorine-containing gas generated in the dechlorination pretreatment section into the absorption tower. The furnace body between the high-temperature pyrolysis section and the catalytic heating stage is equipped with a residue outlet, which is connected to a residue collection device.

10. A method for preparing aviation kerosene from mixed waste plastics through dechlorination-pyrolysis-catalysis, characterized in that... The method utilizes the reaction system as described in claim 9, and the method includes the following steps: (1) Place the waste plastic in the waste plastic raw material silo, and fill the solid acid catalyst in the catalyst fixed bed in the order of quartz wool-catalyst-quartz wool. Turn on the first temperature control device, the second temperature control device, and the third temperature control device so that the temperatures of the dechlorination pretreatment section, the high temperature pyrolysis section, and the catalytic pyrolysis section are 200-360℃, 450-600℃, and 500-650℃, respectively. (2) Open the inert gas inlet and the vacuum pump. Inert gas is introduced into the inert gas inlet to purge the entire reaction system and exhaust the air, so that the reactor is an oxygen-free environment. The waste plastic raw materials in the waste plastic raw material silo are fed into the reactor through the screw feeder. The dechlorination reaction is carried out in the dechlorination pretreatment section. The generated chlorine-containing gas enters the absorption tower. The dechlorinated gas returns to the reactor to participate in the subsequent reaction. (3) The dechlorinated waste plastic is fed into the high-temperature pyrolysis section by a screw feeder, where a high-temperature pyrolysis reaction occurs, generating pyrolysis oil and gas, a small amount of coke, and residue. The pyrolysis oil and gas are carried by the carrier gas into the catalytic pyrolysis section for catalytic pyrolysis. The generated products enter the condensation device and are cooled and liquefied. The liquid fuel products flow into the oil storage tank for collection. The non-condensable pyrolysis gas is discharged from the condensation device and divided into two paths. One path enters the combustion chamber and mixes with air, where it is fully combusted. The generated high-temperature combustion gas is fed into the heat exchange system to provide heat for the entire reaction zone. The other path of non-condensable pyrolysis gas returns to the reactor and enters the catalytic pyrolysis section for hydrogenation enhancement. The solid residue generated during the entire reaction process is collected by the residue collection device and cleaned periodically.

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