Processing method and processing system for rapid liquefaction, pyrolysis and cracking of waste plastics

Abstract

The invention relates to a processing method for quickly liquefying, pyrolyzing and cracking waste plastics, which comprises the following steps of: liquefying the waste plastics to be treated in a waste plastic liquefying unit, and then performing plastic reducing and viscosity breaking treatment in a plastic reducing and viscosity breaking unit to obtain plastic reducing and viscosity breaking liquefied waste plastic oil; the liquefied waste plastic oil obtained after plastic reduction and viscosity reduction cracking enters a heating unit to be heated, and heated liquefied waste plastic oil is obtained; the heated liquefied waste plastic oil enters a pyrolytic reaction unit to be subjected to a pyrolytic reaction, and a pyrolytic product and coke are obtained; the pyrolysis product enters a separation unit for separation treatment; the pyrolysis reaction unit comprises a pyrolysis reactor, the pyrolysis reactor comprises a first reaction area, a transition area and a second reaction area, and a pyrolysis reactor baffle is arranged in the second reaction area. According to the method, the ash content in the pyrolysis oil gas can be reduced, the operation period is prolonged, coke generation is reduced, and large-scale, continuous and green resource recycling of the waste plastics is achieved.

Description

Technical Field

[0001] The present disclosure relates to the field of waste plastic resource recycling, and in particular, to a processing method and a processing system for rapid liquefaction, pyrolysis and cracking of waste plastic. Background Art

[0002] Plastics appear in large quantities in human daily life as packaging materials. Used waste plastics cannot decompose by themselves in nature. Only a few types of waste plastics can be reprocessed and reused through specific recycling channels. A large amount of waste plastics enter landfills in the form of domestic waste. Since waste plastics are not easy to decompose, they occupy a lot of space. The chemical recycling process of waste plastics mainly includes pyrolysis, gasification and ammonia decomposition, among which pyrolysis technology is a hot research direction. The existing waste plastic oil recovery technology mainly includes waste plastic thermal cracking, catalytic thermal cracking and thermal cracking catalytic modification technology. The thermal cracking method has the advantages of simple process, relatively less equipment investment, no need for catalysts, and short reaction process, making the thermal cracking method the lowest unit oil cost compared to the other two technologies. General waste plastics in domestic garbage undergo high-temperature thermal cracking reaction between 380~500℃, with a fast cracking rate and a relatively simple product composition, which can be used as oil products or chemical raw materials.

[0003] CN109401774A discloses a waste plastic continuous pyrolysis system and a pyrolysis method thereof, the system comprising a loading device, a feeding device, a pyrolysis reactor and a slag discharge device connected in sequence. Since the plastic is a macromolecular polymer, a non-Newtonian fluid is formed during the heating process, and a screw propeller is used. The plastic liquefaction process in this process is unevenly heated, and coking and fouling are easily generated. CN112608761A provides a solid heat carrier internal heating type waste plastic treatment process, which solves the problem that the existing waste plastic treatment process is difficult to scale up and has low thermal efficiency by using iron ore pellets as a heat carrier to heat the waste plastic. However, there is no dechlorination means in this process, which makes the impurity content in the pyrolysis oil too high.

[0004] At present, most processes still have the following problems: on the one hand, the pyrolysis reactor used in the waste plastic oil recovery technology has serious entrainment, resulting in a high ash content in the pyrolysis product, which is easy to block the pipeline and the distillation tower filler, resulting in the inability to continue production; on the other hand, the polyvinyl chloride in the waste plastic is decomposed into HCl by heat, which can quickly react with the double bonds in the raw materials to form chlorinated hydrocarbons, making it difficult for traditional reaction devices to efficiently remove chlorine from waste plastics. Waste plastics are high molecular polymers. Due to their huge molecular weight and solid state, the heat transfer inside the plastic is very slow. Traditional heating methods will cause the outside of the plastic to be overheated and cracked, while the inside of the plastic is still solid. As a result, the waste plastic pyrolysis coke rate is high and the gas yield is high. At the same time, the density of the waste plastic is low, and the rate at which the waste plastic enters the reaction device is low. The processing scale of the existing technology is small and cannot meet the needs of modern large-scale recycling. Summary of the invention

[0005] The purpose of the present disclosure is to provide a processing method and system for rapid liquefaction, pyrolysis and cracking of waste plastics, which can effectively realize the resource-based, large-scale and continuous utilization of waste plastics and reduce coke generation.

[0006] In order to achieve the above-mentioned object, the present disclosure provides a first aspect of a processing method for rapid liquefaction, pyrolysis and cracking of waste plastics, the method comprising: S1, allowing the waste plastic to be processed to enter the waste plastic liquefaction unit for liquefaction treatment to obtain liquefied waste plastic; S2, allowing the liquefied waste plastic to enter a plastic reduction and viscosity reduction unit for plastic reduction and viscosity reduction cracking treatment to obtain plastic reduction and viscosity reduction cracked liquefied waste plastic oil; S3, allowing the liquefied waste plastic oil subjected to plastic reduction and visbreaking to enter a material heating unit for heating treatment to obtain high-temperature liquefied waste plastic oil; S4, allowing the high-temperature liquefied waste plastic oil to enter a pyrolysis reaction unit for pyrolysis reaction to obtain pyrolysis products and coke; S5, allowing the pyrolysis product to enter a separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction; Wherein, the pyrolysis reaction unit includes a pyrolysis reactor, and along the material flow direction, the pyrolysis reactor includes a first reaction zone, a transition zone and a second reaction zone which are arranged in sequence.

[0007] Optionally, the shell of the pyrolysis reactor includes, from bottom to top, a first constant diameter cylinder, a second variable diameter cylinder and a third constant diameter cylinder which are sealed and connected in sequence, the first constant diameter cylinder forms the first reaction zone, the second variable diameter cylinder forms the filtration zone, and the third constant diameter cylinder forms the second reaction zone; the first reaction zone, the transition zone and the second reaction zone are sequentially distributed in the inner cavity of the pyrolysis reactor from bottom to top along the axial direction; Optionally, the cross-sections of the first constant diameter cylinder, the second variable diameter cylinder and the third constant diameter cylinder are circular respectively; the inner diameter of the first constant diameter cylinder is smaller than the inner diameter of the third constant diameter cylinder, the bottom cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the first constant diameter cylinder, and the top cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the third constant diameter cylinder; The ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is (1.5-5.0):1; the inner diameter of the third equal-diameter cylinder is 400-10000 mm; the inner diameter of the first equal-diameter cylinder is 300-6000 mm; The ratio of the height of the second diameter-changing cylinder to the bottom cross-sectional diameter is (0.05-2.0): 1, and the angle between the side wall of the second diameter-changing cylinder and the axis of the pyrolysis reactor is 10-80°; The ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is (0.1-1.0):1; the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is (0.1-0.8):1.

[0008] Optionally, the pyrolysis reactor further comprises a baffle, the top edge of which is circumferentially connected to the top edge of the side wall of the third equal-diameter cylinder. Preferably, the baffle has an angle of inclination from the side wall to the central axis of the third equal-diameter cylinder, preferably, with the side wall of the third equal-diameter cylinder as a reference, and the angle is 30-80°; The ratio of the height of the baffle to the cross-sectional diameter of the third equal-diameter cylinder is (0.1-2.5):1.

[0009] Optionally, before step S1, the method further includes: The chlorine-containing waste plastic raw material enters the waste plastic melting and dechlorination unit for melting and dechlorination treatment to obtain a gas phase material containing hydrogen chloride and a dechlorinated waste plastic material; allowing the dechlorinated waste plastic material to enter the waste plastic liquefaction unit; or The dechlorinated waste plastic material is subjected to cooling treatment and crushing treatment in sequence to obtain dechlorinated waste plastic particles; and the dechlorinated waste plastic particles are allowed to enter the waste plastic liquefaction unit.

[0010] Optionally, the method further comprises: The gaseous material containing hydrogen chloride enters a hydrogen chloride absorption unit, contacts with a hydrogen chloride absorbent, and performs hydrogen chloride absorption treatment to obtain a chlorine-containing absorbent and dechlorinated dry gas; Optionally, the gaseous material containing hydrogen chloride enters the hydrogen chloride absorption unit under the action of a vacuum system; Wherein, the hydrogen chloride absorbent is water or an alkali solution with a pH greater than 7; optionally, the alkali solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide solution, sodium bicarbonate solution, sodium carbonate solution and ammonia water.

[0011] Optionally, the waste plastic melting dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw or single-screw conveying device; The process conditions of the melt dechlorination treatment include: a feed rate of 5 to 5000 kg / h, preferably 100 to 4000 kg / h; an outlet temperature of 150 to 370° C., preferably 300 to 330° C., a reaction time of 0.1 to 0.5 h, preferably 0.1 to 0.3 h; a vacuum degree of the waste plastic melt dechlorination unit of 50 to 300 mmHg, preferably 50 to 150 mmHg; Preferably, the particle size of the dechlorinated waste plastic particles obtained by pulverization is 100-2000 μm.

[0012] Optionally, the method further comprises: Returning at least part of the wax oil fraction from the separation unit to the plastic reduction and viscosity reduction unit for recycling; Preferably, the weight ratio of the recycled wax oil fraction to the waste plastic to be treated is (0.2-5.0):1, preferably (0.2-2):1; Preferably, the fraction with a distillation range of more than 350° C. obtained by separation by the separation unit is used as the wax oil fraction.

[0013] Optionally, in step S1, the waste plastic liquefaction unit uses a heating liquefaction conveying device to perform the liquefaction treatment; optionally, the heating liquefaction conveying device includes a first screw-type heating conveying device; preferably, the first screw-type heating conveying device is selected from a twin-screw or single-screw heating conveying device with heating; The process conditions of the liquefaction treatment include: an outlet temperature of 370-500° C., preferably 380-450° C.; a residence time of 5-20 min, preferably 5-15 min.

[0014] Optionally, in step S2, the plastic reduction and viscosity reduction unit uses a plastic reduction and viscosity reduction reactor to perform the plastic reduction and viscosity reduction cracking treatment, and preferably, the plastic reduction and viscosity reduction reactor is an adiabatic plastic reduction and viscosity reduction reactor; Preferably, the process conditions of the plastic reduction and visbreaking treatment include: a reaction temperature of 370-450° C., preferably 380-420° C., more preferably 390-420° C.; and a residence time of 2-120 min, preferably 30-70 min.

[0015] Optionally, in step S3, the material heating unit includes a heating furnace; Preferably, the process conditions of the heating treatment include: the outlet temperature of the heating furnace is 450-550° C., preferably 460-520° C.; optionally, the steam injection amount is 0.5-5% by weight, preferably 1-3% by weight.

[0016] Optionally, in step S4, the process conditions of the pyrolysis reaction include: the top pressure of the pyrolysis tower is 0.05~0.6MPa, preferably 0.1~0.3Mpa; the pyrolysis reaction temperature is 450~580℃, preferably 480~550℃; the operation cycle of the pyrolysis tower is 1~500h, preferably 10~240h.

[0017] Optionally, the waste plastics to be processed include one or more of LDPE, HDPE, PS, PP, PET and PVC; Optionally, the PVC content in the waste plastics to be processed is less than 10% by weight; the ash content in the waste plastics to be processed is 1-40% by weight, preferably 2-30% by weight.

[0018] The second aspect of the present disclosure provides a processing system for rapid liquefaction and pyrolysis and cracking of waste plastics, the processing system comprising: a waste plastic liquefaction unit, a plastic reduction and viscosity reduction unit, a material heating unit, a pyrolysis reaction unit and a separation unit; The waste plastic liquefaction unit comprises an inlet for waste plastic to be processed and an outlet for liquefied waste plastic, and the waste plastic liquefaction unit is configured to liquefy the waste plastic to be processed; The plastic reduction and viscosity reduction unit comprises a liquefied waste plastic inlet and a liquefied waste plastic oil outlet, and the plastic reduction and viscosity reduction unit is configured to perform plastic reduction and viscosity reduction cracking treatment on the liquefied waste plastic; the liquefied waste plastic inlet is connected to the liquefied waste plastic outlet of the waste plastic liquefaction unit; The material heating unit comprises a heating inlet and a heating outlet, and the material heating unit is configured to heat the liquefied waste plastic oil after plastic reduction and viscosity reduction cracking; the heating inlet is connected to the liquefied waste plastic oil outlet of the plastic reduction and viscosity reduction unit; The pyrolysis reaction unit comprises a pyrolysis reactor, and along the material flow direction, the pyrolysis reactor comprises a first reaction zone, a transition zone, and a second reaction zone arranged in sequence; the first reaction zone, the transition zone, and the second reaction zone are axially distributed from bottom to top inside the pyrolysis reactor and are fluidically connected, the pyrolysis reactor comprises a reaction zone inlet and a reaction zone outlet, the reaction zone inlet is connected to the heating outlet of the heating unit, and the pyrolysis reaction unit is configured to perform pyrolysis reaction treatment on high-temperature liquefied waste plastics; The separation unit includes a separation inlet, a dry gas outlet, a liquefied gas outlet, a gasoline fraction outlet, a diesel fraction outlet and a wax oil fraction outlet; the separation inlet is connected to the reaction zone outlet of the pyrolysis reaction unit, and the separation unit is configured to separate and process the pyrolysis products.

[0019] Optionally, the shell of the pyrolysis reactor includes, from bottom to top, a first constant diameter cylinder, a second variable diameter cylinder and a third constant diameter cylinder which are sealed and connected in sequence, the first constant diameter cylinder forms the first reaction zone, the second variable diameter cylinder forms the filtration zone, and the third constant diameter cylinder forms the second reaction zone; Optionally, the cross-sections of the first constant diameter cylinder, the second variable diameter cylinder and the third constant diameter cylinder are circular respectively; the inner diameter of the first constant diameter cylinder is smaller than the inner diameter of the third constant diameter cylinder, the bottom cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the first constant diameter cylinder, and the top cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the third constant diameter cylinder; The ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is (1.5-5.0):1; the inner diameter of the third equal-diameter cylinder is 400-10000 mm; the inner diameter of the first equal-diameter cylinder is 300-6000 mm; the ratio of the height of the second variable-diameter cylinder to the bottom cross-sectional diameter is (0.05-2.0):1, and the angle between the side wall of the second variable-diameter cylinder and the axis of the pyrolysis reactor is 10-80°; the ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is (0.1-1.0):1; the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is (0.1-0.8):1; The pyrolysis reactor further comprises a baffle, the top edge of which is circumferentially connected to the top edge of the side wall of the third equal-diameter cylinder; preferably, the baffle has an angle of inclination from the side wall to the central axis of the third equal-diameter cylinder based on the side wall of the third equal-diameter cylinder; preferably, the angle is 30-80°; the ratio of the height of the baffle to the cross-sectional diameter of the third equal-diameter cylinder is (0.1-2.5): 1; Optionally, the system also includes a waste plastic melting dechlorination unit and a hydrogen chloride absorption unit; The waste plastic melting dechlorination unit comprises an inlet for chlorine-containing waste plastic raw materials, an outlet for gaseous materials containing hydrogen chloride, and an outlet for liquid materials of dechlorinated waste plastics. The waste plastic melting dechlorination unit is configured to perform melting dechlorination treatment on the chlorine-containing waste plastic raw materials; the outlet for liquid materials of dechlorinated waste plastics is connected to an inlet for waste plastics to be treated of the waste plastic liquefaction unit; The hydrogen chloride absorption unit comprises a hydrogen chloride-containing gas phase material inlet, a hydrogen chloride absorbent and a dechlorination dry gas outlet; the hydrogen chloride-containing gas phase material inlet is connected to the hydrogen chloride-containing gas phase material outlet of the waste plastic melting dechlorination unit; Preferably, the waste plastic liquefaction unit comprises a heating liquefaction conveying device; optionally, the heating liquefaction conveying device comprises a first screw-type heating conveying device; preferably, the first screw-type heating conveying device is selected from a twin-screw or single-screw heating conveying device with heating; Preferably, the waste plastic melting dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw or single-screw conveying device; Preferably, the waste plastic reduction and viscosity reduction unit further comprises a circulating oil inlet; the circulating oil inlet is connected to the wax oil fraction outlet of the separation unit; Optionally, the waste plastic melting and dechlorination unit further includes a non-condensable steam outlet.

[0020] Through the above technical scheme, the present invention provides a processing method and processing system for rapid liquefaction and pyrolysis cracking of waste plastics. The present invention obtains liquefied waste plastic oil with plastic reduction and viscous cracking by rapidly liquefying and reducing plastic and viscous cracking the waste plastics to be processed, thereby reducing the viscosity of the liquefied waste plastics without coking and excessive cracking, improving the transportation density of the raw materials, and forming fluidized waste plastics that can be transported by a pump, which is uniform, has good fluidity, and has high liquid thermal conductivity; then, the waste plastics are treated by a heating furnace or the like to quickly reach the pyrolysis reaction temperature, and the heated liquefied waste plastics are transported to a pyrolysis reactor composed of a first reaction zone, a transition zone, and a second reaction zone for pyrolysis reaction, which can effectively make the ash particles settle in the reactor and are difficult to be entrained out of the pyrolysis reactor, significantly reducing the ash content in the pyrolysis oil and gas, thereby preventing pipeline blockage, improving the operation cycle, and reducing coke generation, and being able to obtain a higher liquid yield and a lower coking rate, thereby realizing large-scale, continuous, and green resource recycling of waste plastics.

[0021] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings: Figure 1 It is an exemplary flow chart of the processing method and processing system for rapid liquefaction, pyrolysis and cracking of waste plastics provided in the present disclosure.

[0023] Figure 2 It is a schematic diagram of an exemplary structure inside the pyrolysis reactor provided by the present disclosure.

[0024] Description of Reference Numerals 1-waste plastic storage tank, 2-waste plastic melting and dechlorination unit, 3-waste plastic liquefaction unit, 4-plastic reduction and viscosity reduction reaction unit, 5-heating unit, 6-pyrolysis reaction unit, 7-separation unit, 8-hydrogen chloride absorption unit, 9-pipeline, 10-pipeline, 11-pipeline, 12-pipeline, 13-diesel fraction outlet, 14-liquefied gas and gasoline fraction outlet, 15-wax oil fraction outlet, 16-pipeline, 17-pipeline, 18-dry gas outlet, 19-pipeline, 20-first equal-diameter cylinder, 21-second variable-diameter cylinder, 22-third equal-diameter cylinder, 23-baffle, 24-reaction zone inlet, 25, reaction zone outlet. DETAILED DESCRIPTION

[0025] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0026] The first aspect of the present disclosure provides a method for processing waste plastics by rapid liquefaction, pyrolysis and cracking, the method comprising: S1, allowing the waste plastic to be processed to enter the waste plastic liquefaction unit for liquefaction treatment to obtain liquefied waste plastic; S2, allowing the liquefied waste plastic to enter a plastic reduction and viscosity reduction unit for plastic reduction and viscosity reduction cracking treatment to obtain plastic reduction and viscosity reduction cracked liquefied waste plastic oil; S3, allowing the liquefied waste plastic oil subjected to plastic reduction and visbreaking to enter a material heating unit for heating treatment to obtain heated liquefied waste plastic oil; S4, allowing the heated liquefied waste plastic oil to enter a pyrolysis reaction unit for pyrolysis reaction to obtain pyrolysis products and coke; S5, allowing the pyrolysis product to enter a separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction; Wherein, the pyrolysis reaction unit includes a pyrolysis reactor, and along the material flow direction, the pyrolysis reactor includes a first reaction zone, a transition zone and a second reaction zone which are arranged in sequence.

[0027] The present invention provides a processing method and system for rapid liquefaction and pyrolysis cracking of waste plastics. The present invention obtains liquefied waste plastic oil with plastic reduction and viscous reduction cracking by rapidly liquefying and reducing plastic and viscous cracking the waste plastics to be processed, thereby reducing the viscosity of the liquefied waste plastics without coking and excessive cracking, improving the transportation density of the raw materials, and forming fluidized waste plastics that can be transported by a pump and have uniformity, good fluidity, and high liquid thermal conductivity; then, the liquefied waste plastics are treated by a heating furnace or the like to quickly reach the pyrolysis reaction temperature, and the heated liquefied waste plastics are transported to a pyrolysis reactor composed of a first reaction zone, a transition zone, and a second reaction zone for pyrolysis reaction, so that ash particles can be effectively settled in the reactor and are difficult to be entrained out of the pyrolysis reactor, and the ash content in the pyrolysis oil and gas is significantly reduced, thereby preventing pipeline blockage, improving the operation cycle, and reducing coke generation, so that a higher liquid yield and a lower coking rate can be obtained, and large-scale, continuous, and green resource recycling of waste plastics can be achieved.

[0028] In a specific embodiment, the shell of the pyrolysis reactor includes, from bottom to top, a first equal-diameter cylinder, a second variable-diameter cylinder, and a third equal-diameter cylinder that are sealed and connected, the first equal-diameter cylinder forms the first reaction zone, the second variable-diameter cylinder forms the filtration zone, and the third equal-diameter cylinder forms the second reaction zone; the first reaction zone, the transition zone, and the second reaction zone are distributed in the inner cavity of the pyrolysis reactor in sequence from bottom to top along the axial direction.

[0029] In one embodiment, the cross-sections of the first constant diameter cylinder, the second variable diameter cylinder and the third constant diameter cylinder are respectively circular; the inner diameter of the first constant diameter cylinder is smaller than the inner diameter of the third constant diameter cylinder, the bottom cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the first constant diameter cylinder, and the top cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the third constant diameter cylinder.

[0030] In the above embodiment, a first equal-diameter cylinder, a second variable-diameter cylinder and a third equal-diameter cylinder which are sealed and connected are sequentially arranged from bottom to top in the shell of the pyrolysis reactor, which can effectively adjust the fluidity of the fluidized waste plastics, effectively make the ash particles settle in the reactor and are difficult to be entrained out of the pyrolysis reactor, significantly reducing the ash content in the pyrolysis oil and gas, thereby preventing pipeline blockage, improving the operation cycle, and reducing coke generation, thereby realizing large-scale, continuous, and green resource recycling of waste plastics.

[0031] In a preferred embodiment, the ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is (1.5-5.0):1, preferably (1.5-3.0):1; the inner diameter of the third equal-diameter cylinder is 400-10000 mm, preferably 1000-6000 mm; the inner diameter of the first equal-diameter cylinder is 300-6000 mm, preferably 800-4500 mm; The ratio of the height of the second diameter-reducing cylinder to the bottom cross-sectional diameter is (0.05-2.0):1, preferably (0.1-1.2):1, and the angle between the side wall of the second diameter-reducing cylinder and the axis of the pyrolysis reactor is 10-80°, preferably 30-75°; The ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is (0.1-1.0):1, preferably (0.5-0.8):1; the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is (0.1-0.8):1, preferably (0.1-0.5):1.

[0032] In the present disclosure, the preferred sizes of the first equal-diameter cylinder, the second variable-diameter cylinder and the third equal-diameter cylinder can enable the ash particles to settle effectively in the reactor, further reduce the ash content in the pyrolysis oil and gas, prevent pipeline blockage, further improve the operating cycle, and reduce coke formation.

[0033] In a specific embodiment, the pyrolysis reactor further comprises a baffle, the top edge of the baffle is circumferentially connected to the top edge of the side wall of the third equal-diameter cylinder, preferably, with the side wall of the third equal-diameter cylinder as a reference, the baffle has an angle of inclination from the side wall to the central axis of the third equal-diameter cylinder; preferably, the angle is 30-80°, preferably 30-75°; The ratio of the height of the baffle to the cross-sectional diameter of the third equal-diameter cylinder is (0.1-2.5):1, preferably (0.25-1.5):1.

[0034] In the above embodiment, a baffle is provided in the pyrolysis reactor to further effectively settle the ash particles, making it difficult for the ash to be entrained out of the pyrolysis reactor, thereby preventing pipeline blockage and improving the operation cycle.

[0035] In a preferred embodiment, before step S1, the method further comprises: The chlorine-containing waste plastic raw material enters the waste plastic melting and dechlorination unit for melting and dechlorination treatment to obtain a gas phase material containing hydrogen chloride and a dechlorinated waste plastic material; Allowing the dechlorinated waste plastic material to enter the waste plastic liquefaction unit; or, The dechlorinated waste plastic material is subjected to cooling treatment and crushing treatment in sequence to obtain dechlorinated waste plastic particles; and the dechlorinated waste plastic particles are allowed to enter the waste plastic liquefaction unit.

[0036] In the present disclosure, the melt dechlorination step and the waste plastic liquefaction step can use the same rapid heating liquefaction conveying equipment, or each can use a rapid heating liquefaction conveying equipment; for example, the rapid heating liquefaction conveying equipment is a screw-type heating conveying equipment with heating, etc.

[0037] In the present disclosure, a dedicated device is used to quickly heat polyvinyl chloride to decompose it, and a vacuum method is used to quickly separate the decomposed HCl from the reactor to improve the dechlorination efficiency.

[0038] In one embodiment, the method further comprises: The gaseous material containing hydrogen chloride enters a hydrogen chloride absorption unit, contacts with a hydrogen chloride absorbent, and performs hydrogen chloride absorption treatment to obtain a chlorine-containing absorbent and dechlorinated dry gas; Optionally, the gaseous material containing hydrogen chloride enters the hydrogen chloride absorption unit under the action of a vacuum system.

[0039] The present invention discloses a dechlorination unit for preliminary melting and liquefaction of waste plastics to decompose chlorine in chlorine-containing waste plastic PVC into a gas phase, and can use a vacuum system to quickly separate hydrogen chloride, thereby avoiding secondary reaction of hydrogen chloride, improving the dechlorination efficiency of waste plastics, and reducing the anti-corrosion pressure of subsequent equipment.

[0040] In a specific embodiment, the hydrogen chloride absorbent is water or an alkali solution with a pH greater than 7; optionally, the alkali solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide solution, sodium bicarbonate solution, sodium carbonate solution and ammonia water.

[0041] In a preferred embodiment, the waste plastic melting dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw heating and conveying device or a single-screw heating and conveying device; The process conditions of the melt dechlorination treatment include: a feed rate of 5 to 5000 kg / h, preferably 100 to 4000 kg / h; an outlet temperature of 150 to 370° C., preferably 300 to 330° C., a reaction time of 1 to 30 min, preferably 1 to 20 min; a vacuum degree of the waste plastic melt dechlorination unit of 50 to 300 mmHg, preferably 50 to 150 mmHg; Preferably, the particle size of the dechlorinated waste plastic particles obtained by pulverization is 100-2000 μm, preferably 300-1500 μm.

[0042] In the present disclosure, the apparatus and method for cooling treatment and pulverizing treatment may be conventional apparatus and method in the art.

[0043] In a preferred embodiment, the method further comprises: At least part of the wax oil fraction from the separation unit is returned to the plastic reduction and viscosity reduction unit for recycling.

[0044] In a preferred embodiment, the weight ratio of the recycled wax oil fraction to the liquefied waste plastic is (0.2-5.0):1, preferably (0.2-2.0):1; In a preferred embodiment, the fraction with a distillation range of more than 350°C obtained by the separation unit or the fraction with a distillation range of more than 350°C in other processes is used as the wax oil fraction. Processing according to this embodiment can further improve the utilization efficiency of waste plastic resources; and the introduction of the wax oil fraction into the waste plastic reduction and viscosity reduction unit is also beneficial to the plastic reduction and viscosity reduction cracking treatment of the waste plastic.

[0045] In one embodiment, in step S1, the waste plastic liquefaction unit uses a heating conveying device to perform the liquefaction process; optionally, the heating conveying device includes a first screw heating conveying device; preferably, the first screw heating conveying device is selected from a twin-screw heating conveying device or a single-screw heating conveying device with heating. The rapid heating liquefaction conveying device used in the present disclosure is conducive to the rapid liquefaction process of solid waste plastics.

[0046] In a preferred embodiment, the process conditions of the liquefaction treatment include: an outlet temperature of 370-500° C., preferably 380-450° C.; and a residence time of 1-20 min, preferably 1-15 min.

[0047] In a preferred embodiment, in step S2, the plastic reduction and viscosity reduction unit uses a plastic reduction and viscosity reduction reactor to perform the plastic reduction and viscosity reduction cracking treatment, and preferably, the plastic reduction and viscosity reduction reactor is an adiabatic plastic reduction and viscosity reduction reactor; Preferably, the process conditions of the plastic reduction and visbreaking treatment include: a reaction temperature of 370-450° C., preferably 380-420° C., more preferably 390-420° C.; and a residence time of 2-120 min, preferably 30-70 min.

[0048] In one embodiment, in step S3, the material heating unit includes a heating furnace; In a preferred embodiment, the process conditions of the heat treatment include: the outlet temperature of the heating furnace is 450-550° C., preferably 460-520° C.; optionally, the steam injection amount is 0.5-5% by weight, preferably 1-3% by weight.

[0049] In a preferred embodiment, in step S4, the process conditions of the pyrolysis reaction include: the top pressure of the pyrolysis tower is 0.05~0.6MPa, preferably 0.1~0.3Mpa; the pyrolysis reaction temperature is 450~580℃, preferably 480~550℃; the operation cycle of the pyrolysis tower is 1~500h, preferably 10~240h.

[0050] In the present disclosure, the pyrolysis reaction unit may include a plurality of pyrolysis towers arranged in parallel.

[0051] In one embodiment, the waste plastics to be processed include one or more of LDPE, HDPE, PS, PP, PET and PVC.

[0052] In one embodiment, the PVC content in the waste plastics to be processed is less than 10% by weight; the ash content in the waste plastics to be processed is 1-40% by weight, preferably 2-30% by weight.

[0053] In the present disclosure, the separation process of the separation unit is a conventional method in the art, and may include, for example, distillation, fractionation and rectification to separate different fractions of the pyrolysis product.

[0054] The second aspect of the present disclosure provides a processing system for rapid liquefaction, pyrolysis and cracking of waste plastics, such as Figure 1 As shown, the treatment system includes: a waste plastic liquefaction unit, a plastic reduction and viscosity reduction unit, a material heating unit, a pyrolysis reaction unit and a separation unit; The waste plastic liquefaction unit comprises an inlet for waste plastic to be processed and an outlet for liquefied waste plastic, and the waste plastic liquefaction unit is configured to liquefy the waste plastic to be processed; The plastic reduction and viscosity reduction unit comprises a liquefied waste plastic inlet and a liquefied waste plastic oil outlet, and the plastic reduction and viscosity reduction unit is configured to perform plastic reduction and viscosity reduction cracking treatment on the liquefied waste plastic; the liquefied waste plastic inlet is connected to the liquefied waste plastic outlet of the waste plastic liquefaction unit; The material heating unit comprises a heating inlet and a heating outlet, and the material heating unit is configured to heat the liquefied waste plastic oil after plastic reduction and viscosity reduction cracking; the heating inlet is connected to the liquefied waste plastic oil outlet of the plastic reduction and viscosity reduction unit; The pyrolysis reaction unit comprises a pyrolysis reactor, and along the material flow direction, the pyrolysis reactor comprises a first reaction zone, a transition zone, and a second reaction zone arranged in sequence; the shell of the pyrolysis reactor comprises a first constant diameter cylinder, a second variable diameter cylinder, and a third constant diameter cylinder in a sealed manner from bottom to top, the first constant diameter cylinder forms the first reaction zone, the second variable diameter cylinder forms the filtering zone, and the third constant diameter cylinder forms the second reaction zone; the first reaction zone, the transition zone, and the second reaction zone are sequentially distributed in the inner cavity of the pyrolysis reactor from bottom to top along the axial direction; Optionally, the cross-sections of the first constant diameter cylinder, the second variable diameter cylinder and the third constant diameter cylinder are circular respectively; the inner diameter of the first constant diameter cylinder is smaller than the inner diameter of the third constant diameter cylinder, the bottom cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the first constant diameter cylinder, and the top cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the third constant diameter cylinder; The ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is (1.5-5.0):1, preferably (1.5-3.0):1; the inner diameter of the third equal-diameter cylinder is 400-10000mm, preferably 100-6000mm; the inner diameter of the first equal-diameter cylinder is 300-6000mm, preferably 800-4500mm; the ratio of the height of the second variable-diameter cylinder to the bottom cross-sectional diameter is (0.05-2.0):1 , preferably (0.1-1.2):1, the angle between the side wall of the second variable diameter cylinder and the axis of the pyrolysis reactor is 10-80°, preferably 30-75°; the ratio of the height of the third equal diameter cylinder to the height of the first equal diameter cylinder is (0.1-1.0):1, preferably (0.5-0.8):1; the ratio of the height of the second variable diameter cylinder to the height of the first equal diameter cylinder is (0.1-0.8):1, preferably (0.1-0.5):1; The first reaction zone, the transition zone and the second reaction zone are axially distributed from bottom to top inside the pyrolysis reactor and are fluidically connected. The pyrolysis reactor comprises a reaction zone inlet and a reaction zone outlet. The reaction zone inlet is arranged at the bottom of the first reaction zone, and the reaction zone outlet is arranged at the top of the second reaction zone. The reaction zone inlet is connected to the heating outlet of the heating unit. The pyrolysis reaction unit is configured to perform pyrolysis reaction treatment on the heated liquefied waste plastic. The separation unit includes a separation inlet, a dry gas outlet, a liquefied gas outlet, a gasoline fraction outlet, a diesel fraction outlet and a wax oil fraction outlet; the separation inlet is connected to the reaction zone outlet of the pyrolysis reaction unit, and the separation unit is configured to separate and process the pyrolysis products.

[0055] In one embodiment, the separation unit may include a distillation apparatus, a fractionation apparatus, and a rectification apparatus.

[0056] In one embodiment, if Figure 1As shown, the pyrolysis reactor also includes a baffle, the top edge of which is circumferentially connected to the top edge of the side wall of the third equal-diameter cylinder; preferably, based on the side wall of the third equal-diameter cylinder, the baffle has an angle of inclination from the side wall to the central axis of the third equal-diameter cylinder, preferably, the angle is 30~80°, preferably 30~75°; the ratio of the height of the baffle to the cross-sectional diameter of the third equal-diameter cylinder is (0.1~2.5):1, preferably (0.25~1.5):1.

[0057] The present disclosure provides a specific structure of a pyrolysis reactor using the above specific embodiments, as shown in the attached Figure 2 As shown, the shell of the pyrolysis reactor 6 includes, from bottom to top, a first equal-diameter cylinder 20 (first reaction zone), a second variable-diameter cylinder 21 (transition zone), and a third equal-diameter cylinder 22 (second reaction zone) which are sealed and connected in sequence; the inner cavity of the pyrolysis reactor 6 also includes a baffle 23, and the top edge of the baffle 23 is circumferentially connected to the top edge of the side wall of the third equal-diameter cylinder 22. With the side wall of the third equal-diameter cylinder as a reference, the baffle has an angle of inclination from the side wall to the central axis of the third equal-diameter cylinder, and the angle is 30-80°, preferably 30-75°.

[0058] The process flow of the system provided by the above specific embodiments in the present disclosure specifically includes: Figure 1 As shown: The waste plastics or dehydrated and dechlorinated waste plastic particles stored in the waste plastic storage tank 1 enter the waste plastic melting and dechlorination unit 2, and after dehydration, deaeration and dechlorination, a gaseous material containing hydrogen chloride and a dechlorinated waste plastic material are obtained. The gaseous material containing hydrogen chloride is pumped into the hydrogen chloride absorption unit 8 through a vacuum system to contact with a hydrogen chloride absorbent for hydrogen chloride absorption treatment, thereby obtaining a chlorine-containing absorbent and dechlorinated dry gas. A small amount of non-condensable gas is discharged through pipeline 9, and most of the dechlorinated dry gas is introduced into the dry gas pipeline 19 obtained by the separation unit through pipeline 19. The waste plastic liquefaction unit 3 adopts a heating liquefaction conveying device. The dechlorinated waste plastic liquid phase material from the waste plastic melting and dechlorination unit 2 can be cooled and crushed out of the device to obtain dechlorinated waste plastic particles, or can directly enter the heating liquefaction conveying device 3 (waste plastic liquefaction unit) to obtain a molten dechlorinated waste plastic liquid phase material; the molten dechlorinated waste plastic liquid phase material enters the adiabatic plastic reduction and viscosity reduction reactor 4 (waste plastic reduction and viscosity reduction unit) for plastic reduction and viscosity reduction cracking treatment to obtain a plastic reduction and viscosity reduction cracked liquefied waste plastic oil, or the wax oil fraction from the separation unit 7 can simultaneously enter the adiabatic plastic reduction and viscosity reduction reactor 4 for recycling; the viscerated liquefied waste plastic oil is sent to the heating furnace 5 (heating unit) via the pipeline 10, and after being heated and heated by the heating furnace 5, the heated liquefied waste plastic enters the pyrolysis reactor 6 (pyrolysis reaction unit) via the pipeline 11 for pyrolysis reaction to obtain pyrolysis products and coke; The pyrolysis products enter the subsequent separation unit 7 through pipeline 12 for separation treatment: the dry gas exits the device from pipeline 18, the liquefied gas and gasoline fractions exit the device from pipeline 14, and the diesel fraction exits the device from pipeline 13; the wax oil fraction at the bottom of the tower is led out of the separation unit via pipeline 15, and part of the wax oil fraction can also be returned to the adiabatic plastic reduction and viscosity reduction reactor 4 (waste plastic viscosity reduction unit) via pipeline 17 for recycling, and can also be used as a product lead-out device via pipeline 16.

[0059] The present disclosure is further described in detail by way of examples. The raw materials used in the examples can all be obtained through commercial sources.

[0060] Among them, the rotational viscosity test method was used to test the kinematic viscosity (200°C) of the viscous and cracked liquefied waste plastic oil.

[0061] The analytical method for chlorine content in liquefied waste plastics is: Q / SH 3360 270-2018.

[0062] The analysis methods for other elements in liquefied waste plastics are: carbon and hydrogen elements SH / T 0656-2017, oxygen element SH / T 0986, nitrogen element SH / T 0704-2010, and sulfur element SH / T 0842-2010.

[0063] The distribution of pyrolysis reaction products was obtained by simulated distillation NB / SH / T 0829-2010 method.

[0064] The density analysis method of naphtha, diesel and wax oil is SH / T0604-2000; the gas composition in the pyrolysis reaction product is determined by the RIPP 78-90 method; the hydrocarbon composition of naphtha, diesel, etc. is determined by chromatography analysis.

[0065] In the following examples, the particle size of the particles obtained by the pulverization process ranges from 100 to 2000 μm.

[0066] Example 1 The process system of this embodiment includes: a waste plastic storage tank 1, a waste plastic melting and dechlorination unit 2, a waste plastic liquefaction unit 3, a plastic reduction and viscosity reduction unit 4, a heating unit 5, a pyrolysis reaction unit 6, a separation unit 7 and a hydrogen chloride absorption unit 8.

[0067] The pyrolysis reaction unit adopts a pyrolysis reactor, and along the material flow direction, the pyrolysis reactor includes a first reaction zone, a transition zone and a second reaction zone arranged in sequence; The shell of the pyrolysis reactor includes, from bottom to top, a first constant diameter cylinder, a second variable diameter cylinder and a third constant diameter cylinder that are sealed and connected in sequence, the first constant diameter cylinder forms a first reaction zone, the second variable diameter cylinder forms a filtering zone, and the third constant diameter cylinder forms a second reaction zone; the first reaction zone, the transition zone and the second reaction zone are sequentially distributed in the inner cavity of the pyrolysis reactor from bottom to top along the axial direction; The cross sections of the first equal diameter cylinder, the second variable diameter cylinder and the third equal diameter cylinder are circular respectively; the inner diameter of the first equal diameter cylinder is smaller than the inner diameter of the third equal diameter cylinder, the bottom cross section diameter of the second variable diameter cylinder is the same as the inner diameter of the first equal diameter cylinder, and the top cross section diameter of the second variable diameter cylinder is the same as the inner diameter of the third equal diameter cylinder; The ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is 2:1; the inner diameter of the third equal-diameter cylinder is 1600 mm; the inner diameter of the first equal-diameter cylinder is 800 mm; the ratio of the height of the second variable-diameter cylinder to the bottom cross-sectional diameter is 1.17:1, and the angle between the side wall of the second variable-diameter cylinder and the axis of the pyrolysis reactor is 55°; the ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is 0.5:1; the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is 0.5:1; The pyrolysis reactor also includes a baffle, the top edge of which is circumferentially connected to the top edge of the side wall of the third equal-diameter cylinder, and the angle between the baffle and the side wall of the third equal-diameter cylinder is 30°; the ratio of the height of the baffle to the cross-sectional diameter of the third equal-diameter cylinder is 0.25:1.

[0068] Waste agricultural film (mainly made of PE, with a chlorine content of 0.0162% by weight) is sent to the waste plastic melting dechlorination unit for melting dechlorination treatment. During the dechlorination process, the gas phase material containing hydrogen chloride is extracted by a vacuum system and sent to the hydrogen chloride absorption unit to contact with the hydrogen chloride absorbent (NaOH solution) for hydrogen chloride absorption treatment. The waste plastic melting dechlorination unit uses a second twin-screw heating and conveying device and a vacuum device connected to the second twin-screw heating and conveying device. The feed rate is about 100kg / h, the outlet temperature is 220℃, the reaction time is 6min, the vacuum degree of the second twin-screw heating and conveying device is 150mmHg, the screw diameter of the second twin-screw heating and conveying device is 65mm, and the outlet pressure of the second screw heating and conveying device is 0.2MPa. The waste plastic material is cooled and crushed to obtain dechlorinated waste plastic particles WP-1. The properties of the obtained dechlorinated waste plastic particles WP-1 are shown in Table 1.

[0069] The dechlorinated waste plastic particles WP-1 are sent to the first twin-screw heating and conveying equipment for liquefaction treatment. The liquefied waste plastic has an outlet temperature of 400°C, a residence time of 6 minutes, a feed rate of 100 kg / h, a screw diameter of 65 mm, and an outlet pressure of 0.2 MPa. The liquefied waste plastic is sent to an adiabatic plastic reduction and viscosity reduction reactor for plastic reduction and viscosity reduction cracking treatment to obtain a plastic reduction and viscosity reduction liquefied waste plastic oil. The reaction temperature is 400°C, and samples are taken at residence times of 30 minutes, 50 minutes, and 70 minutes, respectively, and are recorded as WP-1-30, WP-1-50, and WP-1-70. The rotational viscosity of the samples is measured, and the test results are shown in Table 2.

[0070] The liquefied waste plastic oil with reduced plasticity and viscosity is sent to a heating unit (heating furnace) for heating treatment to obtain heated liquefied waste plastic. The heating temperature is 520°C, the residence time is 50 minutes, and the steam injection amount in the heating furnace is 0.5% by weight. The heated liquefied waste plastic is then sent to a pyrolysis reaction unit (pyrolysis tower) for reaction. The top pressure of the pyrolysis tower is 0.15 MPa, the reaction temperature is 480°C, and the operation cycle is 10 hours (pyrolysis tower switching operation time) to obtain pyrolysis products and coke.

[0071] The pyrolysis products were separated into dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction by distillation tower. Product distribution test was carried out, and the distribution of pyrolysis reaction products is shown in Table 4.

[0072] Comparative Example 1 The raw materials and waste plastic melting dechlorination equipment and method of Example 1 were used, except that the outlet temperature was set to 250°C and the residence time was 0.1h. The morphology of the waste plastic after transportation under different outlet temperature conditions was tested to obtain liquefied waste plastic WP-1-1, and its properties are listed in Table 2.

[0073] WP-1-1 was heated to 250°C by a screw heating and conveying device and directly squeezed into a normal pressure container with an internal temperature of 250°C and a gas outlet. The temperature was kept for 60 minutes, and a sample WP-1-1-60 was taken to test the viscosity. Its viscosity was too large and exceeded the measurement range. Its form was a plastic solid and could not flow by itself, indicating the necessity of deplasticizing and reducing the viscosity of waste plastics. The purpose is to reduce the viscosity of liquefied waste plastics without coking and excessive cracking, so as to form uniform and fluidized waste plastics that can be transported by a pump.

[0074] Example 2 The process system of this embodiment includes: a waste plastic storage tank 1, a waste plastic melting and dechlorination unit 2, a waste plastic liquefaction unit 3, a plastic reduction and viscosity reduction unit 4, a heating unit 5, a pyrolysis reaction unit 6, a separation unit 7 and a hydrogen chloride absorption unit 8.

[0075] The pyrolysis reaction unit adopts a pyrolysis reactor, and along the material flow direction, the pyrolysis reactor includes a first reaction zone, a transition zone and a second reaction zone arranged in sequence; The shell of the pyrolysis reactor includes, from bottom to top, a first constant diameter cylinder, a second variable diameter cylinder and a third constant diameter cylinder that are sealed and connected in sequence, the first constant diameter cylinder forms a first reaction zone, the second variable diameter cylinder forms a filtering zone, and the third constant diameter cylinder forms a second reaction zone; the first reaction zone, the transition zone and the second reaction zone are sequentially distributed in the inner cavity of the pyrolysis reactor from bottom to top along the axial direction; The cross sections of the first equal diameter cylinder, the second variable diameter cylinder and the third equal diameter cylinder are circular respectively; the inner diameter of the first equal diameter cylinder is smaller than the inner diameter of the third equal diameter cylinder, the bottom cross section diameter of the second variable diameter cylinder is the same as the inner diameter of the first equal diameter cylinder, and the top cross section diameter of the second variable diameter cylinder is the same as the inner diameter of the third equal diameter cylinder; The ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is 1.8:1; the inner diameter of the third equal-diameter cylinder is 1440 mm; the inner diameter of the first equal-diameter cylinder is 800 mm; the ratio of the height of the second variable-diameter cylinder to the bottom cross-sectional diameter is 0.4:1, and the angle between the side wall of the second variable-diameter cylinder and the axis of the pyrolysis reactor is 45°; the ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is 0.5:1; the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is 0.3:1; The pyrolysis reactor also includes a baffle, the top edge of which is circumferentially connected to the top edge of the side wall of the third equal-diameter cylinder, and the angle between the baffle and the side wall of the third equal-diameter cylinder is 50°; the ratio of the height of the baffle to the cross-sectional diameter of the third equal-diameter cylinder is 0.625:1.

[0076] The real waste plastic (plastic from a landfill plant, made of chlorine-containing mixed plastic, with a chlorine content of about 3% by weight) was fed into the waste plastic melting dechlorination unit for melting dechlorination treatment. The second twin-screw heating and conveying equipment used in the waste plastic melting dechlorination unit was the same as that in Example 1. The feed rate was about 100 kg / h, the outlet temperature was 300°C, the reaction time was 6 min, the vacuum degree of the second twin-screw heating and conveying equipment was 70 mmHg, and dechlorinated waste plastic particles WP-2 were obtained. The properties of the obtained dechlorinated waste plastic particles WP-2 are shown in Table 3. The absorption process of the hydrogen chloride-containing gas obtained by the dechlorination treatment was the same as that in Example 1.

[0077] The dechlorinated waste plastic particles WP-2 were sent to the first twin-screw heating and conveying equipment for liquefaction treatment. The liquefied waste plastics obtained had an outlet temperature of 420°C, a residence time of 12 min, a feed rate of 100 kg / h, a screw diameter of 65 mm, and an outlet pressure of 0.2 MPa for the first screw heating and conveying equipment. The liquefied waste plastics were sent to an adiabatic plastic reduction and viscosity reduction reactor for plastic reduction and viscosity reduction cracking treatment to obtain plastic reduction and viscosity reduction liquefied waste plastic oil. The reaction temperature was 420°C, the residence time was 30 min, and the WP-2-30 sample was taken to measure the rotational viscosity. The test results are shown in Table 2.

[0078] The liquefied waste plastic oil with reduced plasticity and viscosity is sent to the heating unit (heating furnace) for heating treatment to obtain heated liquefied waste plastic, the heating temperature is 500℃, the residence time is 50min, and the steam injection amount in the heating furnace is 0.5wt%; then the obtained heated liquefied waste plastic is sent to the pyrolysis reaction unit (pyrolysis tower) for reaction, the top pressure of the pyrolysis tower is 0.15MPa, the reaction temperature is 480℃, the operation cycle is 10h (pyrolysis tower switching operation time), and pyrolysis reaction products and coke are obtained. The pyrolysis reaction products are separated by a distillation tower to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. The distribution of pyrolysis reaction products is shown in Table 4.

[0079] Comparative Example 2 The process system of Example 2 is adopted, with the only difference that the first reaction zone, transition zone, second reaction zone and baffle are not arranged inside the pyrolysis reactor, and the pyrolysis reactor is only a conventional cylindrical reactor, wherein the inner diameter of the reactor is 800 mm and the outer diameter is 815 mm; the height of the reactor is 5040 mm; and the pressure inside the reactor is 0.15 MPa.

[0080] Referring to the process flow of Example 2, the same waste plastic raw material was used, and the specific process conditions were the same as those of Example 2. The distribution of pyrolysis reaction products is shown in Table 4.

[0081] Comparative Example 3 The process system of Example 2 is adopted, with the only difference that the first reaction zone, the transition zone, and the second reaction zone are not arranged in the pyrolysis reactor, and the pyrolysis reactor is a conventional cylindrical reactor including a baffle, wherein the angle between the baffle and the side wall of the cylinder in the reactor and the height of the baffle are the same as those in Example 1, and the specifications and dimensions of the reactor are the same as those in Comparative Example 2.

[0082] Referring to the process flow of Example 2, the same waste plastic raw material was used, and the specific process conditions were the same as those of Example 2. The distribution of pyrolysis reaction products is shown in Table 4.

[0083] Example 3 The process system of Example 1 is adopted, and the dechlorinated waste plastic particles WP-1 obtained in Example 1 are liquefied in the first twin-screw heating and conveying equipment to obtain liquefied waste plastic. The outlet temperature of the liquefied waste plastic is 400°C, the residence time is 12min, and the feed rate is 100kg / h. The first twin-screw heating and conveying equipment is the same as that in Example 1.

[0084] The obtained liquefied waste plastics are sent to an adiabatic plastic reduction and viscosity reduction reactor for plastic reduction and viscosity reduction cracking treatment. The temperature of the adiabatic plastic reduction and viscosity reduction reactor is 380° C., and the residence time is 1 hour to obtain liquefied waste plastic oil with plastic reduction and viscosity reduction.

[0085] The liquefied waste plastic oil with reduced plasticity and viscosity is sent to a heating unit (heating furnace) for heating treatment to obtain heated liquefied waste plastic, with an outlet temperature of 520°C, a residence time of 50 minutes, and a steam injection amount of 0.5% by weight in the heating furnace; the obtained heated liquefied waste plastic is then sent to a pyrolysis reaction unit (pyrolysis tower) for reaction, with a top pressure of 0.15 MPa, a pyrolysis reaction temperature of 520°C, and an operation cycle of 16 hours (pyrolysis tower switching operation time) to obtain pyrolysis reaction products and coke.

[0086] The pyrolysis reaction products are separated by a distillation tower to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. The distribution of pyrolysis products is shown in Table 5, the distribution of gas phase products is shown in Table 7, and the liquid phase products are cut to obtain naphtha, diesel and wax oil components, whose properties are shown in Table 8, and the properties of coke products are shown in Table 9.

[0087] Example 4 The process system of Example 3 is used, except that no baffle is provided inside the pyrolysis reactor. Referring to the process flow and method of Example 3, the same waste plastic raw material was used, and the specific process conditions were the same as those of Example 3 to obtain pyrolysis reaction products and coke. The pyrolysis reaction products were separated by a distillation tower to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. The distribution of pyrolysis reaction products is shown in Table 5.

[0088] Example 5 The process system of Example 3 is used, with the only difference being that the angle between the baffle inside the pyrolysis reactor and the side wall of the third equal-diameter cylinder is 20°.

[0089] Referring to the process flow and method of Example 3, the same waste plastic raw material was used, and the specific process conditions were the same as those of Example 3 to obtain pyrolysis reaction products and coke. The pyrolysis reaction products were separated by a distillation tower to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. The distribution of pyrolysis reaction products is shown in Table 5.

[0090] Example 6 The process system of Example 3 is adopted, with the only difference that the ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is 2.5:1; the ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is 0.05:1; and the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is 0.05:1.

[0091] Referring to the process flow and method of Example 3, the same waste plastic raw material was used, and the specific process conditions were the same as those of Example 3 to obtain pyrolysis reaction products and coke. The pyrolysis reaction products were separated by a distillation tower to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. The distribution of pyrolysis reaction products is shown in Table 5.

[0092] Example 7 The method, process system and raw materials of Example 3 are adopted, except that the pressure at the top of the pyrolysis tower is 0.08 MPa, the reaction temperature is 450°C, and the operation cycle is 5 hours (pyrolysis tower switching operation time), to obtain pyrolysis reaction products and coke. The pyrolysis reaction products are separated by a distillation tower to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. The distribution of pyrolysis reaction products is shown in Table 6.

[0093] Example 8 The method, process system and raw materials of Example 3 are adopted, except that the pressure at the top of the pyrolysis tower is 0.01 MPa, the reaction temperature is 400°C, and the operation cycle is 10 hours (pyrolysis tower switching operation time), to obtain pyrolysis reaction products and coke. The pyrolysis reaction products are separated by a distillation tower to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. The distribution of pyrolysis reaction products is shown in Table 6.

[0094] Example 9 The method, process system and raw materials of Example 3 are used, the only difference being the operating conditions of the melt dechlorination treatment, specifically including: the reaction time is 2 minutes.

[0095] The dechlorinated waste plastic particles WP-9 were sent to the first twin-screw heating and conveying equipment for liquefaction treatment to obtain liquefied waste plastic. The outlet temperature of the liquefied waste plastic was 390°C, the residence time was 2 minutes, and it was kept at 390°C for 70 minutes. The rotational viscosity was measured by sampling (recorded as WP-9-70) to obtain viscous and broken liquefied waste plastic oil. The viscosity results of the viscous and broken liquefied waste plastic oil are shown in Table 2.

[0096] The cracking reaction conditions were the same as those in Example 3, and the product distribution of the cracking reaction products is shown in Table 6.

[0097] Table 1 Properties of waste agricultural film particles

[0098] Table 2 Viscosity of plastics with reduced plasticity and viscosity

[0099] According to the data in Table 2, when the plastic reduction and viscosity reduction treatment meets the reaction temperature of 390-420℃ and the residence time of 30-70min, different viscosity reduction temperatures have different optimal viscosity reduction times. As the viscosity decreases, the ash distribution in the plastic reduction and viscosity reduction plastic changes.

[0100] Table 3 Properties of dechlorinated waste plastic particles

[0101] Table 4 Distribution of waste plastic pyrolysis products

[0102] Table 5 Distribution of waste plastic pyrolysis products

[0103] Table 6 Distribution of waste plastic pyrolysis products

[0104] Table 7 Distribution of gas phase products in the pyrolysis reaction products of Example 3

[0105] Table 8 Properties of the liquid products in the pyrolysis reaction products of Example 3

[0106] Table 9 Properties of coke products from Example 3

[0107] As can be seen from Example 1, the waste agricultural film is subjected to hot melt dechlorination treatment by a twin-screw heating and conveying device to obtain the dechlorinated waste plastic WP-1. Since most of the chlorine in the waste agricultural film is inorganic chlorine, it is not decomposed into hydrogen chloride during the dechlorination process, but enters into the dechlorinated waste plastic WP-1, so the chlorine content of WP-1 does not change. After the dechlorinated waste plastic WP-1 is subjected to plastic reduction and viscosity reduction in a plastic reduction and viscosity reduction reactor, the viscosity at 200°C is reduced to 267.6cp, and the sample has a stable flow state. After graded heating and mixing, it is sent to the pyrolysis tower provided in Example 1 for pyrolysis reaction, and the dry gas, liquefied gas, gasoline, diesel, wax oil and coke are obtained by fractionation in a fractionation tower with yields of 1.61%, 2.54%, 15.15%, 40.06%, 32.22% and 8.26%.

[0108] As can be seen from Example 2, after the real waste plastic with high chlorine content is subjected to hot melt dechlorination treatment by a twin-screw heating and conveying device, most of the chlorine in the waste plastic is removed; after the dechlorinated waste plastic WP-2 is reduced in plasticity and viscosity at 420°C for 30 minutes, the viscosity at 200°C is reduced to 282.8cp, and the sample has a stable flow state. After graded heating and mixing, it is sent to the pyrolysis tower provided in Example 2 for pyrolysis reaction, and the dry gas, liquefied gas, gasoline, diesel, wax oil and coke are obtained by fractionation in a fractionation tower with yields of 5.39%, 4.89%, 24.32%, 23.21%, 10.91% and 20.96% respectively. Since the waste plastic contains a certain amount of polyester, and after long-term oxidation, the raw material contains a certain amount of oxygen, so the pyrolysis product contains a certain amount of CO and CO2.

[0109] Comparing Examples 1 and 2 with Comparative Examples 2 and 3, it can be seen that, combined with the data in Table 4, the solid content of the wax oil fraction in the pyrolysis reaction product obtained by the processing method for rapid liquefaction, pyrolysis and cracking of waste plastics provided by the present disclosure is only 0.01% and 0.017%, achieving a good solid removal effect. As can be seen from Comparative Example 2, the process system and raw materials of Example 2 are adopted, because the pyrolysis reactor used is only a conventional cylindrical reactor, which leads to the inability to effectively settle the ash particles in the reactor, and it is easy to be entrained out of the pyrolysis reactor, the ash content in the pyrolysis oil gas increases, and the solid content in the wax oil fraction is higher than that in Examples 1 and 2. As can be seen from Comparative Example 3, the process system and raw materials of Example 2 are adopted, because the pyrolysis reactor is a conventional cylindrical reactor including a baffle, the ash particles cannot be effectively settled in the reactor only by the baffle, resulting in an increase in the ash content in the pyrolysis oil gas, and the solid content in the wax oil fraction is higher than that in Examples 1 and 2.

[0110] As can be seen from Example 3, after the waste agricultural film is processed by the process provided by the present disclosure, the liquid yield (including liquefied gas) of pyrolysis can reach 87.43%, and the coke yield is relatively small. The properties of the obtained naphtha, diesel and wax oil show that the ash content of each fraction oil is low, the mass fraction of hydrogen element is high, the mass fraction of olefins is high, the mass fraction of aromatics is low, and the content of chlorine and silicon heteroatoms is low, and it can be directly sent to the refinery for post-processing. The solid content in the wax oil fraction is only 0.007%. The sum of the mass fractions of trienes in the pyrolysis gas is high (>45% by weight), and the ash content of coke is as high as 50.5% by weight, which cannot be sold as a product and can be used as a boiler fuel for blending.

[0111] By comparing Example 3 with Examples 4 to 6, it can be seen that, combined with the data in Table 5, since the internal structure of the pyrolysis reactor provided in Examples 4 to 6 is not within the scope of the present disclosure, the ash particles cannot be effectively settled in the reactor and are easily entrained out of the pyrolysis reactor, resulting in an increase in the ash content in the pyrolysis oil and gas, causing pipeline blockage, and coking in the reactor, thereby increasing the coke content in the pyrolysis reaction product, and the total liquid yield is also reduced.

[0112] Combined with the data in Table 6, by comparing Example 3 with Examples 7 and 8, it can be seen that controlling the pyrolysis reaction conditions within the preferred range and limited range of the present disclosure can further reduce the solid content and coke content in the wax oil fraction in the pyrolysis reaction product, and further improve the liquid yield; by comparing Example 3 with Example 9, it can be seen that controlling the melt dechlorination treatment within the preferred range of the present disclosure can further reduce the solid content in the wax oil fraction in the pyrolysis reaction product, and further improve the liquid yield.

[0113] The preferred embodiments of the present disclosure are described in detail above; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0114] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0115] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for rapidly liquefying and pyrolyzing waste plastics, characterized in that: The method includes: S1, allowing the waste plastic to be processed to enter the waste plastic liquefaction unit for liquefaction treatment to obtain liquefied waste plastic; S2, allowing the liquefied waste plastic to enter a plastic reduction and viscosity reduction unit for plastic reduction and viscosity reduction cracking treatment to obtain plastic reduction and viscosity reduction cracked liquefied waste plastic oil; S3, allowing the liquefied waste plastic oil subjected to plastic reduction and visbreaking to enter a material heating unit for heating treatment to obtain heated liquefied waste plastic oil; S4, allowing the heated liquefied waste plastic oil to enter a pyrolysis reaction unit for pyrolysis reaction to obtain pyrolysis products and coke; S5, allowing the pyrolysis product to enter a separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction; Wherein, the pyrolysis reaction unit includes a pyrolysis reactor, and along the material flow direction, the pyrolysis reactor includes a first reaction zone, a transition zone and a second reaction zone which are arranged in sequence.

2. The processing method according to claim 1, characterized in that: The shell of the pyrolysis reactor includes, from bottom to top, a first constant diameter cylinder, a second variable diameter cylinder and a third constant diameter cylinder which are sealed and connected in sequence, the first constant diameter cylinder forms the first reaction zone, the second variable diameter cylinder forms the filtering zone, and the third constant diameter cylinder forms the second reaction zone; the first reaction zone, the transition zone and the second reaction zone are sequentially distributed in the inner cavity of the pyrolysis reactor from bottom to top along the axial direction; Optionally, the cross-sections of the first constant diameter cylinder, the second variable diameter cylinder and the third constant diameter cylinder are circular respectively; the inner diameter of the first constant diameter cylinder is smaller than the inner diameter of the third constant diameter cylinder, the bottom cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the first constant diameter cylinder, and the top cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the third constant diameter cylinder; Preferably, the ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is (1.5-5.0):1; the inner diameter of the third equal-diameter cylinder is 400-10000 mm; the inner diameter of the first equal-diameter cylinder is 300-6000 mm; Preferably, the ratio of the height of the second diameter-reducing cylinder to the bottom cross-sectional diameter is (0.05-2.0): 1, and the angle between the side wall of the second diameter-reducing cylinder and the axis of the pyrolysis reactor is 10-80°; Preferably, the ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is (0.1-1.0):1; the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is (0.1-0.8):

1.

3. The processing method according to claim 1, characterized in that: The pyrolysis reactor further comprises a baffle, the top edge of which is circumferentially connected to the top edge of the side wall of the third equal-diameter cylinder; preferably, with the side wall of the third equal-diameter cylinder as a reference, the baffle has an angle of inclination from the side wall to the central axis of the third equal-diameter cylinder, preferably, the angle is 30-80°; The ratio of the height of the baffle to the cross-sectional diameter of the third equal-diameter cylinder is (0.1-2.5):

1.

4. The processing method according to claim 1, characterized in that: Before step S1, the method further comprises: The chlorine-containing waste plastic raw material enters the waste plastic melting and dechlorination unit for melting and dechlorination treatment to obtain a gas phase material containing hydrogen chloride and a dechlorinated waste plastic material; The dechlorinated waste plastic material is allowed to enter the waste plastic liquefaction unit; or, the dechlorinated waste plastic material is cooled and crushed in sequence to obtain dechlorinated waste plastic particles; and the dechlorinated waste plastic particles are allowed to enter the waste plastic liquefaction unit.

5. The processing method according to claim 4, characterized in that: The method further includes: The gaseous material containing hydrogen chloride enters a hydrogen chloride absorption unit, contacts with a hydrogen chloride absorbent, and performs hydrogen chloride absorption treatment to obtain a chlorine-containing absorbent and dechlorinated dry gas; Optionally, the gaseous material containing hydrogen chloride enters the hydrogen chloride absorption unit under the action of a vacuum system; Wherein, the hydrogen chloride absorbent is water or an alkali solution with a pH greater than 7; optionally, the alkali solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide solution, sodium bicarbonate solution, sodium carbonate solution and ammonia water.

6. The processing method according to claim 4, characterized in that: The waste plastic melting dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw heating and conveying device or a single-screw heating and conveying device; The process conditions of the melt dechlorination treatment include: a feed rate of 5 to 5000 kg / h, preferably 100 to 4000 kg / h; an outlet temperature of 150 to 370° C., preferably 300 to 330° C., a reaction time of 1 to 30 min, preferably 1 to 20 min; a vacuum degree of the waste plastic melt dechlorination unit of 50 to 300 mmHg, preferably 50 to 150 mmHg; Preferably, the particle size of the dechlorinated waste plastic particles obtained by pulverization is 100-2000 μm.

7. The processing method according to claim 1, characterized in that: The method further includes: Returning at least part of the wax oil fraction from the separation unit to the plastic reduction and viscosity reduction unit for recycling; Preferably, the weight ratio of the recycled wax oil fraction to the waste plastic to be treated is (0.2-5.0):1, preferably (0.2-2):1; Preferably, the fraction with a distillation range of more than 350° C. obtained by separation by the separation unit is used as the wax oil fraction.

8. The processing method according to claim 1, characterized in that: In step S1, the waste plastic liquefaction unit uses a heating liquefaction conveying device to perform the liquefaction treatment; optionally, the heating liquefaction conveying device includes a first screw-type heating conveying device; preferably, the first screw-type heating conveying device is selected from a twin-screw heating conveying device with heating or a single-screw heating conveying device; The process conditions of the liquefaction treatment include: an outlet temperature of 370-500° C., preferably 380-450° C.; a residence time of 1-20 min, preferably 1-15 min.

9. The processing method according to claim 1, characterized in that: In step S2, the plastic reduction and viscosity reduction unit uses a plastic reduction and viscosity reduction reactor to perform the plastic reduction and viscosity reduction cracking treatment, and preferably, the plastic reduction and viscosity reduction reactor is an adiabatic plastic reduction and viscosity reduction reactor; Preferably, the process conditions of the plastic reduction and visbreaking treatment include: a reaction temperature of 370-450° C., preferably 380-420° C., more preferably 390-420° C.; and a residence time of 2-120 min, preferably 30-70 min.

10. The processing method according to claim 1, characterized in that: In step S3, the material heating unit includes a heating furnace; Preferably, the process conditions of the heating treatment include: the outlet temperature of the heating furnace is 450-550° C., preferably 460-520° C.; optionally, the steam injection amount is 0.5-5% by weight, preferably 1-3% by weight.

11. The processing method according to claim 1, characterized in that: In step S4, the process conditions of the pyrolysis reaction include: the top pressure of the pyrolysis tower is 0.05~0.6MPa, preferably 0.1~0.3Mpa; the pyrolysis reaction temperature is 450~580℃, preferably 480~550℃; the operation cycle of the pyrolysis tower is 1~500h, preferably 10~240h.

12. The processing method according to claim 1, characterized in that: The waste plastics to be processed include one or more of LDPE, HDPE, PS, PP, PET and PVC; Optionally, the PVC content in the waste plastics to be processed is less than 10% by weight; the ash content in the waste plastics to be processed is 1-40% by weight, preferably 2-30% by weight.

13. A processing system for rapid liquefaction, pyrolysis and cracking of waste plastics, characterized in that: The treatment system includes: a waste plastic liquefaction unit, a plastic reduction and viscosity reduction unit, a material heating unit, a pyrolysis reaction unit and a separation unit; The waste plastic liquefaction unit comprises an inlet for waste plastic to be processed and an outlet for liquefied waste plastic, and the waste plastic liquefaction unit is configured to liquefy the waste plastic to be processed; The plastic reduction and viscosity reduction unit comprises a liquefied waste plastic inlet and a liquefied waste plastic oil outlet, and the plastic reduction and viscosity reduction unit is configured to perform plastic reduction and viscosity reduction cracking treatment on the liquefied waste plastic; the liquefied waste plastic inlet is connected to the liquefied waste plastic outlet of the waste plastic liquefaction unit; The material heating unit comprises a heating inlet and a heating outlet, and the material heating unit is configured to heat the liquefied waste plastic oil after plastic reduction and viscosity reduction cracking; the heating inlet is connected to the liquefied waste plastic oil outlet of the plastic reduction and viscosity reduction unit; The pyrolysis reaction unit comprises a pyrolysis reactor, and along the material flow direction, the pyrolysis reactor comprises a first reaction zone, a transition zone, and a second reaction zone arranged in sequence; the first reaction zone, the transition zone, and the second reaction zone are axially distributed from bottom to top inside the pyrolysis reactor and are fluidically connected, the pyrolysis reactor comprises a reaction zone inlet and a reaction zone outlet, the reaction zone inlet is arranged at the bottom of the first reaction zone, the reaction zone outlet is arranged at the top of the second reaction zone, the reaction zone inlet is connected to the heating outlet of the heating unit, and the pyrolysis reaction unit is configured to perform pyrolysis reaction treatment on the heated liquefied waste plastic; The separation unit includes a separation inlet, a dry gas outlet, a liquefied gas outlet, a gasoline fraction outlet, a diesel fraction outlet and a wax oil fraction outlet; the separation inlet is connected to the reaction zone outlet of the pyrolysis reaction unit, and the separation unit is configured to separate and process the pyrolysis products.

14. The processing system according to claim 13, characterized in that: The shell of the pyrolysis reactor includes, from bottom to top, a first constant diameter cylinder, a second variable diameter cylinder and a third constant diameter cylinder that are sealed and connected in sequence, the first constant diameter cylinder forms the first reaction zone, the second variable diameter cylinder forms the filtering zone, and the third constant diameter cylinder forms the second reaction zone; Optionally, the cross-sections of the first constant diameter cylinder, the second variable diameter cylinder and the third constant diameter cylinder are circular respectively; the inner diameter of the first constant diameter cylinder is smaller than the inner diameter of the third constant diameter cylinder, the bottom cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the first constant diameter cylinder, and the top cross-sectional diameter of the second variable diameter cylinder is the same as the inner diameter of the third constant diameter cylinder; Optionally, the ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is (1.5-5.0):1; the inner diameter of the third equal-diameter cylinder is 400-10000 mm; the inner diameter of the first equal-diameter cylinder is 300-6000 mm; the ratio of the height of the second variable-diameter cylinder to the bottom cross-sectional diameter is (0.05-2.0):1, and the angle between the side wall of the second variable-diameter cylinder and the axis of the pyrolysis reactor is 10-80°; the ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is (0.1-1.0):1; the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is (0.1-0.8):1; Optionally, the pyrolysis reactor further comprises a baffle, the top edge of which is circumferentially connected to the top edge of the side wall of the third equal-diameter cylinder; preferably, with the side wall of the third equal-diameter cylinder as a reference, the baffle has an angle of inclination from the side wall to the central axis of the third equal-diameter cylinder; preferably, the angle is 30-80°; the ratio of the height of the baffle to the cross-sectional diameter of the third equal-diameter cylinder is (0.1-2.5): 1; Optionally, the system also includes a waste plastic melting dechlorination unit and a hydrogen chloride absorption unit; The waste plastic melting dechlorination unit comprises an inlet for chlorine-containing waste plastic raw materials, an outlet for gaseous materials containing hydrogen chloride, and an outlet for liquid materials of dechlorinated waste plastics. The waste plastic melting dechlorination unit is configured to perform melting dechlorination treatment on the chlorine-containing waste plastic raw materials; the outlet for liquid materials of dechlorinated waste plastics is connected to an inlet for waste plastics to be treated of the waste plastic liquefaction unit; The hydrogen chloride absorption unit comprises a hydrogen chloride-containing gas phase material inlet, a hydrogen chloride absorbent and a dechlorination dry gas outlet; the hydrogen chloride-containing gas phase material inlet is connected to the hydrogen chloride-containing gas phase material outlet of the waste plastic melting dechlorination unit; Preferably, the waste plastic liquefaction unit comprises a heating liquefaction conveying device; optionally, the heating liquefaction conveying device comprises a first screw-type heating conveying device; preferably, the first screw-type heating conveying device is selected from a twin-screw heating conveying device with heating or a single-screw heating conveying device; Preferably, the waste plastic melting dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw heating and conveying device or a single-screw heating and conveying device; Preferably, the waste plastic reduction and viscosity reduction unit further comprises a circulating oil inlet; the circulating oil inlet is connected to the wax oil fraction outlet of the separation unit; Optionally, the waste plastic melting and dechlorination unit further includes a non-condensable steam outlet.

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