Treatment method and treatment system for viscosity reduction pyrolysis cracking of waste plastics

Abstract

The invention relates to a waste plastic viscosity reduction pyrolysis cracking treatment method which comprises the following steps: sequentially feeding waste plastic to be treated into a waste plastic liquefaction unit, a waste plastic reduction and viscosity reduction unit, a material heating unit and a pyrolysis reaction unit for treatment to obtain a pyrolysis mixed product; the pyrolysis mixed product enters an inertial separation unit for gas-solid separation treatment, and a pyrolysis product is obtained; the pyrolysis product enters a product separation unit to be subjected to separation treatment, and dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction are obtained; the pyrolytic reaction unit comprises a pyrolytic reaction device, and the pyrolytic reaction device comprises a reaction area, a necking area and an outlet area which are sequentially arranged in the material flowing direction. The solid content of the liquid phase product and the ash content of the coke product can be further reduced, blockage of an inlet pipeline and the interior of the product separation unit is prevented, the operation period is prolonged, coke generation is reduced, and large-scale, continuous and green resource recycling of 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 treatment method and system for waste plastic viscosity reduction and thermal decomposition and cracking. Background Art

[0002] At present, a large amount of waste plastics enters landfills in the form of domestic garbage. Since waste plastics are not easy to decompose, they occupy a lot of space. Especially in recent years, the amount of waste plastics generated has increased, and it has become an urgent task to quickly and greenly recycle waste plastics.

[0003] The existing treatment of waste plastics mainly focuses on the resource utilization of waste plastics through waste plastic oil recovery technology, and waste plastic oil recovery technology mainly includes waste plastic thermal cracking, catalytic thermal cracking and thermal cracking catalytic modification technology. Among them, the thermal cracking method has simple process, relatively less equipment investment, no catalyst, short reaction process, fast cracking speed, relatively simple product composition, and can be used as oil or chemical raw materials.

[0004] CN112608761A provides a solid heat carrier internal heat 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, the process still has problems such as polyvinyl chloride in the waste plastic being 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 the traditional reaction device to efficiently remove chlorine from the waste plastic, resulting in too high an impurity content in the pyrolysis oil. And because the waste plastic belongs to a high molecular weight polymer, due to the huge molecular weight and being solid, the heat transfer inside the plastic is very slow, and the traditional heating method will cause the plastic to be overheated and cracked, while the inside of the plastic is still solid, resulting in a high pyrolysis coke rate of the waste plastic and a high gas yield. At the same time, the density of the waste plastic is low, the rate at which the waste plastic enters the reaction device is low, and the processing scale of the existing technology is small, which cannot meet the needs of modern large-scale recycling. Summary of the invention

[0005] The purpose of the present disclosure is to provide a treatment method and system for waste plastic viscosity reduction thermal decomposition and cracking, 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 treatment method for waste plastics by reducing viscosity and thermal 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 the waste plastic deplasticization and viscosity reduction unit for plastic deplasticization and viscosity reduction treatment to obtain liquefied waste plastic oil after plastic deplasticization and viscosity reduction; S3, allowing the liquefied waste plastic oil subjected to plastic reduction and viscous cracking 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 a first pyrolysis product and coke; S5, allowing the first pyrolysis product to enter an inertial separation unit for gas-solid separation treatment to obtain a second pyrolysis product; S6, allowing the second pyrolysis product to enter a product separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction; Wherein, the pyrolysis reaction unit comprises a pyrolysis reaction device, and along the material flow direction, the pyrolysis reaction device comprises a reaction zone, a necking zone and an outlet zone which are arranged in sequence.

[0007] Optionally, the shell of the pyrolysis reaction device 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 reaction zone, the second variable diameter cylinder forms the necking zone, and the third constant diameter cylinder forms the outlet 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 larger 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; wherein the diameter of the first constant diameter cylinder is larger than the 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 (0.01-0.2):1, preferably (0.01-0.15):1; further preferably, the inner diameter of the third equal-diameter cylinder is 5-800 mm, preferably 10-500 mm; the inner diameter of the first equal-diameter cylinder is 500-10000 mm, preferably 500-6000 mm; The ratio of the height of the second diameter-changing cylinder to the bottom cross-sectional diameter is (0.1-4.0):1, preferably (0.2-3.0):1; the angle between the side wall of the second diameter-changing cylinder and the axis of the pyrolysis reaction device is 10-80°, preferably 30-75°; The ratio of the height of the second variable diameter cylinder to the height of the first constant diameter cylinder is (0.1-0.8):1, preferably (0.1-0.5):1; 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 (0.1-0.5):1.

[0008] Optionally, before step S1, the method further includes: The chlorine-containing waste plastic raw material enters the waste plastic preliminary melting and liquefaction dechlorination unit for hot melt 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.

[0009] 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.

[0010] Optionally, the method further comprises: Returning at least part of the wax oil fraction from the product separation unit to the waste 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 of the product separation unit is used as the wax oil fraction.

[0011] 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.

[0012] Optionally, the waste plastic preliminary melting, liquefaction and 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.

[0013] Optionally, in step S2, the waste plastics 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.

[0014] 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.

[0015] 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 450~520℃, preferably 480~520℃; the operation cycle of the pyrolysis tower is 1~500h, preferably 10~240h.

[0016] Optionally, in step S5, the inertial separation unit uses a cyclone separation device to perform gas-solid separation processing; The cyclone separation device comprises 1 to 4 groups of cyclone separator assemblies connected in parallel, and each group of cyclone separator assemblies comprises 1 to 3 stages of cyclone separators connected in series; The dust removal efficiency of the cyclone separation device is above 95%, and the pressure drop is below 1500Pa.

[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 3-30% by weight.

[0018] The second aspect of the present disclosure provides a waste plastic viscosity reduction pyrolysis cracking treatment system, the treatment system comprising: a waste plastic liquefaction unit, a waste plastic plastic reduction and viscosity reduction unit, a material heating unit, a pyrolysis reaction unit, an inertial separation unit and a product 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 waste plastic deplasticization and viscosity reduction unit comprises a liquefied waste plastic inlet and a liquefied waste plastic oil outlet, and the plastic deplasticization and viscosity reduction unit is configured to perform plastic deplasticization 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, wherein the heating inlet is connected to the liquefied waste plastic oil outlet of the plastic reduction and viscosity reduction unit, and the material heating unit is configured to heat the liquefied waste plastic oil after plastic reduction and viscosity reduction. The pyrolysis reaction unit comprises a pyrolysis reaction device, and along the material flow direction, the pyrolysis reaction device comprises a reaction zone, a necking zone and an outlet zone arranged in sequence; The reaction zone, the necking zone and the second reaction zone are axially distributed from bottom to top inside the pyrolysis reactor and are fluidically connected. The pyrolysis reaction unit includes a first pyrolysis reactant inlet and a first pyrolysis product outlet. The first pyrolysis reactant inlet is connected to the heating outlet of the material heating unit. The pyrolysis reaction unit is configured to perform pyrolysis reaction treatment on high-temperature liquefied waste plastics. The inertial separation unit comprises a second pyrolysis product inlet and a second pyrolysis product outlet, wherein the second pyrolysis product inlet is connected to the first pyrolysis product outlet of the pyrolysis reaction unit, and the inertial separation unit is configured to perform high-temperature gas-solid separation on the high-temperature pyrolysis product; The product separation unit includes a product 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 product separation inlet is connected to the second pyrolysis product outlet of the inertial separation unit, and the separation unit is configured to separate and process the pyrolysis products after gas-solid separation.

[0019] Optionally, the shell of the pyrolysis reaction device 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 reaction zone, the second variable diameter cylinder forms the necking zone, and the third constant diameter cylinder forms the outlet 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 larger 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; wherein the diameter of the first constant diameter cylinder is larger than the 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 (0.01-0.2):1, preferably (0.01-0.15):1; further preferably, the inner diameter of the third equal-diameter cylinder is 5-800 mm, preferably 10-500 mm; the inner diameter of the first equal-diameter cylinder is 500-10000 mm, preferably 500-6000 mm; the ratio of the height of the second variable-diameter cylinder to the bottom cross-sectional diameter is (0.1-4.0) :1, preferably (0.2-3.0):1; the angle between the side wall of the second variable diameter cylinder and the axis of the pyrolysis reaction device is 10-80°, preferably 30-75°; the ratio of the height of the second variable diameter cylinder to the height of the first constant diameter cylinder is (0.1-0.8):1, preferably (0.1-0.5):1; the ratio of the height of the third constant diameter cylinder to the height of the first constant diameter cylinder is (0.1-1.0):1, preferably (0.1-0.5):1; The inertial separation unit uses a cyclone separation device to perform gas-solid separation processing; Preferably, the cyclone separation device comprises 1 to 4 groups of cyclone separator assemblies connected in parallel, and each group of cyclone separator assemblies comprises 1 to 3 stages of cyclone separators connected in series.

[0020] Optionally, the system also includes a waste plastic preliminary melting, liquefaction and dechlorination unit and a hydrogen chloride absorption unit; The waste plastic preliminary melting and liquefaction dechlorination unit comprises a chlorine-containing waste plastic raw material inlet, a hydrogen chloride-containing gas phase material outlet and a dechlorinated waste plastic liquid phase material outlet, and the waste plastic preliminary melting and liquefaction dechlorination unit is configured to perform hot melt dechlorination treatment on the chlorine-containing waste plastic raw material; the dechlorinated waste plastic liquid phase material outlet is connected to the waste plastic to be treated inlet 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 preliminary melting and liquefaction dechlorination unit; Preferably, the waste plastic liquefaction includes a heating liquefaction conveying device; 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; Preferably, the waste plastic preliminary melting, liquefaction and 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 product separation unit; Optionally, the waste plastic preliminary melting, liquefaction and dechlorination unit further includes a non-condensable steam outlet.

[0021] Through the above technical scheme, the present disclosure provides a treatment method and treatment system for reducing viscosity of waste plastics by pyrolysis and cracking. The present disclosure obtains liquefied waste plastic oil with reduced plastic and reduced viscosity by rapidly liquefying and reducing plastic and cracking the waste plastics to be treated, thereby reducing the viscosity of the liquefied waste plastics without coking and excessive cracking, improving the conveying density of the raw materials, and forming fluidized waste plastics that can be conveyed by a pump and have uniformity, good fluidity, and 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 conveyed to a pyrolysis reaction device for pyrolysis reaction; by adding a necking zone to the pyrolysis reaction device, the ash passes through the necking zone and then enters the inertial separation unit, so that the solid phase material and the ash can be separated separately, and the solid content of the liquid phase product and the ash content of the coke product are further reduced, and the product separation unit inlet pipeline and internal blockage are prevented, thereby improving the operation cycle; in addition, after the waste plastics are liquefied, the conveying density of the raw materials is greatly increased compared with that of the solid waste plastics, and large-scale, continuous, and green resource recycling of the waste plastics can be achieved.

[0022] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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 treatment method and treatment system for viscosity reduction and thermal cracking of waste plastics provided in the present disclosure.

[0024] Figure 2 It is a schematic diagram of an exemplary structure inside the pyrolysis reactor provided by the present disclosure.

[0025] Description of Reference Numerals 1-waste plastic storage tank, 2-waste plastic preliminary melting, liquefaction and dechlorination unit, 3-waste plastic liquefaction unit, 4-waste plastic reduction and viscosity reduction reaction unit, 5-heating unit, 6-pyrolysis reaction unit, 7-inertial separation unit, 8-product separation unit, 9-hydrogen chloride absorption unit, 10-pipeline, 11-pipeline, 12-pipeline, 13-pipeline, 14-pipeline, 15-diesel fraction outlet, 16-liquefied gas and gasoline fraction outlet, 17-wax oil fraction outlet, 18-pipeline, 19-dry gas outlet, 20-pipeline, 21-pipeline, 22-reaction zone, 23-necking zone, 24-export zone. DETAILED DESCRIPTION

[0026] 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.

[0027] The first aspect of the present disclosure provides a method for treating waste plastics by reducing viscosity through thermal decomposition and cracking, the method comprising the following steps: 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 the waste plastic deplasticization and viscosity reduction unit for plastic deplasticization and viscosity reduction treatment to obtain liquefied waste plastic oil after plastic deplasticization and viscosity reduction; 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 a pyrolysis mixed product; S5, allowing the pyrolysis mixed product to enter an inertial separation unit for gas-solid separation treatment to obtain a pyrolysis product; S6, allowing the pyrolysis product to enter a product separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction; Wherein, the pyrolysis reaction unit comprises a pyrolysis reaction device, and along the material flow direction, the pyrolysis reaction device comprises a reaction zone, a necking zone and an outlet zone which are arranged in sequence.

[0028] The present invention obtains liquefied waste plastic oil with plastic reduction, viscosity reduction and cracking by rapidly liquefying and reducing plastic and viscous cracking the waste plastic to be treated, thereby reducing the viscosity of the liquefied waste plastic without coking and excessive cracking, improving the conveying density of the raw materials, and forming fluidized waste plastic with uniformity, good fluidity and high liquid thermal conductivity that can be conveyed by a pump; then, the waste plastic is treated by a heating furnace or the like to quickly reach the pyrolysis reaction temperature, and the heated liquefied waste plastic is conveyed to a pyrolysis reaction device for pyrolysis reaction; a necking zone is added to the pyrolysis reaction device so that the ash passes through the necking zone and then enters the inertial separation unit, so that the solid phase material and the ash can be separated separately, and the solid content of the liquid phase product and the ash content of the coke product are further reduced, so as to prevent the inlet pipeline and the internal part of the product separation unit from being blocked, and improve the operation cycle; in addition, after the waste plastic is liquefied, the conveying density of the raw materials is greatly increased compared with that of the solid waste plastic, so that large-scale, continuous and green resource recycling of the waste plastic can be realized.

[0029] In a specific embodiment, the shell of the pyrolysis reaction device 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 reaction zone, the second variable diameter cylinder forms the necking zone, and the third constant diameter cylinder forms the outlet zone; In one embodiment, the cross-sections of the first constant diameter cylinder, the second variable diameter cylinder and the third constant diameter cylinder are circular; the inner diameter of the first constant diameter cylinder is greater 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; wherein the diameter of the first constant diameter cylinder is greater than the 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 (0.01-0.2):1, preferably (0.01-0.15):1; the inner diameter of the third equal-diameter cylinder is 5-800 mm, preferably 10-500 mm; the inner diameter of the first equal-diameter cylinder is 500-10000 mm, preferably 500-6000 mm; The ratio of the height of the second diameter-changing cylinder to the bottom cross-sectional diameter is (0.1-4.0):1, preferably (0.2-3.0):1; the angle between the side wall of the second diameter-changing cylinder and the axis of the pyrolysis reaction device is 10-80°, preferably 30-75°; The ratio of the height of the second variable diameter cylinder to the height of the first constant diameter cylinder is (0.1-0.8):1, preferably (0.1-0.5):1; 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 (0.1-0.5):1.

[0030] In the above embodiment, the shell of the pyrolysis reaction device includes a first equal-diameter cylinder, a second variable-diameter cylinder and a third equal-diameter cylinder which are sealed and connected in sequence from bottom to top, so that the ash passes through the necking area and then enters the inertial separation unit, thereby realizing the separate separation of solid-phase ash, further reducing the solid content in the liquid phase product and the ash content in the coke product, effectively preventing the inlet pipeline and internal blockage of the product separation unit, improving the operation cycle, and realizing large-scale, continuous, and green resource recycling of waste plastics.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] In a preferred embodiment, the method further comprises: Returning at least part of the wax oil fraction from the product separation unit to the waste plastic reduction and viscosity reduction unit for recycling; In a preferred embodiment, 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; In a preferred embodiment, the fraction with a distillation range of more than 350°C obtained by the product separation unit is used as the wax oil fraction. Processing according to this embodiment can further improve the utilization efficiency of waste plastic resources; and introducing 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 waste plastics.

[0037] 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.

[0038] 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.

[0039] In a preferred embodiment, the waste plastic preliminary melting, liquefaction and 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 hot 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 preliminary melting and liquefaction 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.

[0040] In the present disclosure, the apparatus and method for cooling treatment and pulverizing treatment may be conventional apparatus and method in the art.

[0041] In a preferred embodiment, in step S2, the waste plastics 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; In a preferred embodiment, 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.

[0042] 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.

[0043] 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 450~520℃, preferably 480~520℃; the operation cycle of the pyrolysis tower is 1~500h, preferably 10~240h.

[0044] In the present disclosure, the pyrolysis reaction unit may include a plurality of pyrolysis towers arranged in parallel.

[0045] In one embodiment, in step S5, the inertial separation unit uses a cyclone separation device to perform gas-solid separation to remove solid particulate coke in the pyrolysis mixed product to obtain a pyrolysis product.

[0046] In one embodiment, the cyclone separation device comprises 1 to 4 groups of cyclone separator assemblies connected in parallel, preferably 2 to 4 groups, and each group of cyclone separator assemblies comprises 1 to 3 stages of cyclone separators connected in series, preferably 2 to 3 stages; The dust removal efficiency of the cyclone separation device is above 95%, preferably above 97%, and the pressure drop is below 1500 Pa, preferably below 1200 Pa.

[0047] In the present disclosure, the inertial separation unit refers to a device that uses the inertia of particles or droplets entrained in the airflow to perform gas-solid separation. The inertial separation device used in the present disclosure can be any device used in the inertial separation technology known in the art.

[0048] In one embodiment, the waste plastics to be processed include one or more of LDPE, HDPE, PS, PP, PET and PVC.

[0049] 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 3-30% by weight.

[0050] In the present disclosure, the separation process of the product 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.

[0051] The second aspect of the present disclosure provides a waste plastic viscosity reduction pyrolysis cracking treatment system, the treatment system comprising: a waste plastic liquefaction unit, a waste plastic plastic reduction and viscosity reduction unit, a material heating unit, a pyrolysis reaction unit, an inertial separation unit and a product 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 waste plastic deplasticization and viscosity reduction unit comprises a liquefied waste plastic inlet and a liquefied waste plastic oil outlet, and the plastic deplasticization and viscosity reduction unit is configured to perform plastic deplasticization 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, wherein the heating inlet is connected to the liquefied waste plastic oil outlet of the plastic reduction and viscosity reduction unit, and the material heating unit is configured to heat the liquefied waste plastic oil after plastic reduction and viscosity reduction. The pyrolysis reaction unit comprises a pyrolysis reaction device, and along the material flow direction, the pyrolysis reaction device comprises a reaction zone, a necking zone and an outlet zone arranged in sequence; The reaction zone, the necking zone and the outlet zone are axially distributed from bottom to top inside the pyrolysis reactor and are fluidically connected. The pyrolysis reaction unit includes a pyrolysis mixed reactant inlet and a pyrolysis mixed product outlet. The pyrolysis mixed reactant inlet is arranged at the bottom of the reaction zone, and the pyrolysis mixed product outlet is arranged at the top of the outlet zone. The pyrolysis mixed reactant inlet is connected to the heating outlet of the material heating unit. The pyrolysis reaction unit is configured to perform pyrolysis reaction treatment on the heated liquefied waste plastic; The inertial separation unit comprises a pyrolysis mixed product inlet, a solid outlet and a gas outlet, wherein the pyrolysis mixed product inlet is connected to the pyrolysis mixed product outlet of the pyrolysis reaction unit, and the inertial separation unit is configured to perform high-temperature gas-solid separation on the high-temperature pyrolysis product to remove solid particles; The product separation unit includes a product 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 product separation inlet is connected to the gas outlet of the inertial separation unit, and the product separation unit is configured to separate and process the pyrolysis products after gas-solid separation.

[0052] In one embodiment, if Figure 2 As shown, the shell of the pyrolysis reaction device 6 includes, from bottom to top, a first constant diameter cylinder 22, a second variable diameter cylinder 23 and a third constant diameter cylinder 24 which are sealed and connected in sequence. The first constant diameter cylinder 22 forms the reaction zone, the second variable diameter cylinder 23 forms the necking zone, and the third constant diameter cylinder 24 forms the outlet zone. In one embodiment, the cross-sections of the first constant diameter cylinder, the second variable diameter cylinder and the third constant diameter cylinder are circular; the inner diameter of the first constant diameter cylinder is larger 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; wherein the diameter of the first constant diameter cylinder is larger than the 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 (0.01-0.2):1, preferably (0.01-0.15):1; further preferably, the inner diameter of the third equal-diameter cylinder is 5-800 mm, preferably 10-500 mm; the inner diameter of the first equal-diameter cylinder is 500-10000 mm, preferably 500-6000 mm; the ratio of the height of the second variable-diameter cylinder to the bottom cross-sectional diameter is (0.1-4.0):1 , preferably (0.2~3.0):1; the angle between the side wall of the second variable diameter cylinder and the axis of the pyrolysis reaction device is 10~80°, preferably 30~75°; the ratio of the height of the second variable diameter cylinder to the height of the first constant diameter cylinder is (0.1~0.8):1, preferably (0.1~0.5):1; the ratio of the height of the third constant diameter cylinder to the height of the first constant diameter cylinder is (0.1~1.0):1, preferably (0.1~0.5):1; The inertial separation unit uses a cyclone separation device to perform gas-solid separation processing; The cyclone separation device comprises 1 to 4 groups of cyclone separator assemblies connected in parallel, preferably 2 to 4 groups, and each group of cyclone separator assemblies comprises 1 to 3 stages of cyclone separators connected in series, preferably 2 to 3 stages.

[0053] In one embodiment, the product separation unit may include a distillation device, a fractionation device and a rectification device.

[0054] In one embodiment, the system further comprises a waste plastic preliminary melting, liquefaction and dechlorination unit and a hydrogen chloride absorption unit; The waste plastic preliminary melting and liquefaction dechlorination unit comprises a chlorine-containing waste plastic raw material inlet, a hydrogen chloride-containing gas phase material outlet and a dechlorinated waste plastic liquid phase material outlet, and the waste plastic preliminary melting and liquefaction dechlorination unit is configured to perform hot melt dechlorination treatment on the chlorine-containing waste plastic raw material; the dechlorinated waste plastic liquid phase material outlet is connected to the waste plastic to be treated inlet 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 preliminary melting and liquefaction dechlorination unit; Preferably, the waste plastic liquefaction includes a heating liquefaction conveying device; 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; Preferably, the waste plastic preliminary melting, liquefaction and 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 product separation unit; Optionally, the waste plastic preliminary melting, liquefaction and dechlorination unit further comprises a non-condensable gas outlet, and the non-condensable gas outlet is arranged at the top of the waste plastic preliminary melting, liquefaction and dechlorination unit.

[0055] 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 reaction device 6 includes, from bottom to top, a first constant diameter cylinder 22 (reaction zone), a second variable diameter cylinder 23 (neck zone) and a third constant diameter cylinder 24 (exit zone) which are sealed and connected.

[0056] 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 preliminary melting, liquefaction 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 9 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, and a small amount of non-condensable gas is discharged through a pipeline 10. The waste plastic liquefaction unit adopts a rapid heating liquefaction conveying device 3. The dechlorinated waste plastic liquid phase material from the waste plastic preliminary melting liquefaction dechlorination unit 2 can be discharged from the device for cooling and crushing to obtain dechlorinated waste plastic particles, or can directly enter the rapid 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 plastic reduction and viscosity reduction cracked liquefied waste plastic oil, or the wax oil fraction from the separation unit 8 can simultaneously enter the adiabatic plastic reduction and viscosity reduction reactor 4 for recycling; the plastic reduction and viscosity reduction cracked liquefied waste plastic oil is sent to the heating unit 11 through the pipeline 11. Furnace 5 (heating unit), after being heated by heating furnace 5, the heated liquefied waste plastic enters pyrolysis reaction unit 6 through pipeline 12 for pyrolysis reaction to obtain pyrolysis products and coke; the pyrolysis products enter the subsequent inertial separation unit 7 through pipeline 13 for high-temperature gas-solid separation, and then enter the product separation unit 8 through pipeline 14 for separation treatment: wherein, dry gas exits the device from pipeline 19, liquefied gas and gasoline fractions exit the device from pipeline 16, and diesel fraction exits the device from pipeline 15; the wax oil fraction at the bottom of the tower is led out of the separation unit through pipeline 17, wherein part of the wax oil fraction can also be returned to the adiabatic plastic reduction and viscosity reduction reactor 4 (waste plastic reduction and viscosity reduction unit) through pipeline 20 for recycling, and can also be used as a product leading device through pipeline 18.

[0057] 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.

[0058] Among them, the analysis method for chlorine content in liquefied waste plastics is: Q / SH 3360 270-2018.

[0059] 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.

[0060] The distribution of pyrolysis reaction products was obtained by simulated distillation NB / SH / T 0829-2010 method.

[0061] 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.

[0062] In the following examples, the particle size of the particles obtained by the pulverization process ranges from 100 to 2000 μm.

[0063] Example 1 The process system of this embodiment includes: a waste plastic storage tank 1, a waste plastic preliminary melting, liquefaction and dechlorination unit 2, a waste plastic liquefaction unit 3, a waste plastic reduction and viscosity reduction unit 4, a heating unit 5, a pyrolysis reaction unit 6, an inertial separation unit 7, a product separation unit 8 and a hydrogen chloride absorption unit 9.

[0064] The pyrolysis reaction unit adopts a pyrolysis reaction device, and along the material flow direction, the pyrolysis reaction device includes a reaction zone, a necking zone and an outlet zone arranged in sequence; The shell of the pyrolysis reaction device 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 reaction zone, the second variable diameter cylinder forms a necking zone, and the third constant diameter cylinder forms an outlet zone; 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 larger than the inner diameter of the third equal-diameter cylinder, the bottom cross-sectional diameter of the second variable-diameter cylinder is the same as the inner diameter of the first equal-diameter cylinder, and the top cross-sectional diameter of the second variable-diameter cylinder is the same as the inner diameter of the third equal-diameter cylinder; the reaction zone, the necking zone and the outlet zone are sequentially distributed in the inner cavity of the pyrolysis reactor from bottom to top along the axial direction; the ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is 0.1:1; the inner diameter of the third equal-diameter cylinder is 80mm; the inner diameter of the first equal-diameter cylinder is 800mm; the ratio of the height of the second variable-diameter cylinder to the bottom cross-sectional diameter is 0.78:1, and the angle between the side wall of the second variable-diameter cylinder and the axis of the pyrolysis reaction device is 30°; the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is 0.4:1; the ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is 0.3:1; The inertial separation unit adopts a cyclone separator. The cyclone separation device includes three sets of parallel cyclone separator assemblies. Each set of cyclone separator assemblies includes two stages of cyclone separators. After calculation, the separation efficiency is 97.2% and the pressure drop is 873Pa.

[0065] The waste agricultural film (chlorine content is 0.147 weight %) is fed into the waste plastic preliminary melting and liquefaction dechlorination unit for melting and dechlorination treatment. The waste plastic preliminary melting and liquefaction dechlorination unit adopts a twin-screw heating and conveying equipment and a vacuum device connected to the twin-screw heating and conveying equipment. The feed rate is about 100 kg / h, the outlet temperature is 220°C, the processing time is 6 min, the vacuum degree of the twin-screw heating and conveying equipment is 150 mmHg, the screw diameter of the twin-screw heating and conveying equipment is 65 mm, and the outlet pressure of the twin-screw heating and conveying equipment is 0.2 MPa. Waste plastic DCl-1 is obtained. The properties of the obtained waste plastic particles DCl-1 are shown in Table 1.

[0066] In the dechlorination process, the gaseous material containing hydrogen chloride is extracted by a vacuum system and sent to a hydrogen chloride absorption unit to contact with a hydrogen chloride absorbent (NaOH solution) for hydrogen chloride absorption treatment.

[0067] The DCl-1 was fed into a screw heating and conveying device for liquefaction treatment. The liquefied waste plastic obtained had a heating temperature of 400°C, a heating 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.

[0068] 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 plastic reduction and viscosity reduction liquefied waste plastic oil, the reaction temperature is 400°C, the residence time is 50 minutes, and the plastic reduction and viscosity reduction liquefied waste plastic oil is sent to a heating unit (heating furnace) for heating treatment to obtain heated liquefied waste plastic, the heating temperature is 500°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 sent to the pyrolysis reaction device. The top pressure of the pyrolysis tower is 0.15Mpa, the reaction temperature is 480℃, and the operation cycle is 10h (switching operation time of the pyrolysis tower) to obtain pyrolysis reaction products and coke.

[0069] The obtained pyrolysis reaction products are sent to an inertial separation unit (the cyclone separation device includes 3 sets of parallel cyclone separator assemblies, and each set of cyclone separator assemblies includes 2-stage cyclone separators) for gas-solid separation treatment. The separated pyrolysis reaction products are sent to a product separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. The product distribution test is carried out. The distribution of pyrolysis reaction products is shown in Table 2.

[0070] Example 2 The process system of this embodiment includes: a waste plastic storage tank 1, a waste plastic preliminary melting, liquefaction and dechlorination unit 2, a waste plastic liquefaction unit 3, a waste plastic reduction and viscosity reduction unit 4, a heating unit 5, a pyrolysis reaction unit 6, an inertial separation unit 7, a product separation unit 8 and a hydrogen chloride absorption unit 9.

[0071] The pyrolysis reaction unit adopts a pyrolysis reaction device, and along the material flow direction, the pyrolysis reaction device includes a reaction zone, a necking zone and an outlet zone arranged in sequence; The shell of the pyrolysis reaction device 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 reaction zone, the second variable diameter cylinder forms a necking zone, and the third constant diameter cylinder forms an outlet zone; 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 larger than the inner diameter of the third equal-diameter cylinder, the bottom cross-sectional diameter of the second variable-diameter cylinder is the same as the inner diameter of the first equal-diameter cylinder, and the top cross-sectional diameter of the second variable-diameter cylinder is the same as the inner diameter of the third equal-diameter cylinder; the reaction zone, the necking zone and the outlet zone are sequentially distributed in the inner cavity of the pyrolysis reactor from bottom to top along the axial direction; the ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is 0.1:1; the inner diameter of the third equal-diameter cylinder is 80mm; the inner diameter of the first equal-diameter cylinder is 800mm; the ratio of the height of the second variable-diameter cylinder to the bottom cross-sectional diameter is 0.45:1, and the angle between the side wall of the second variable-diameter cylinder and the axis of the pyrolysis reaction device is 45°; the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is 0.4:1; the ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is 0.3:1; The inertial separation unit adopts a cyclone separator, which is the same cyclone separation device as that used in Example 1, with a separation efficiency of 96.5% and a pressure drop of 964Pa.

[0072] Real waste plastics (chlorine content is about 3 weight %) are fed into the waste plastic preliminary melting and liquefaction dechlorination unit for melting and dechlorination treatment. The waste plastic preliminary melting and liquefaction dechlorination unit adopts a twin-screw heating and conveying equipment and a vacuum device connected to the twin-screw heating and conveying equipment. The feed rate is about 100kg / h, the outlet temperature is 300°C, the processing time is 6min, the vacuum degree of the screw heating and conveying equipment is 70mmHg, the screw diameter of the twin-screw heating and conveying equipment is 65mm, and the outlet pressure of the twin-screw heating and conveying equipment is 0.2MPa to obtain liquefied dechlorinated waste plastics.

[0073] In the dechlorination process, the gaseous material containing hydrogen chloride is extracted by a vacuum system and sent to a hydrogen chloride absorption unit to contact with a hydrogen chloride absorbent (NaOH solution) for hydrogen chloride absorption treatment.

[0074] The liquefied dechlorinated waste plastic is fed into a screw heating and conveying device for liquefaction treatment. The obtained liquefied waste plastic has a heating temperature of 420°C, a heating time of 12 minutes, a feed rate of 100 kg / h, a screw diameter of 65 mm, and an outlet pressure of 0.2 MPa.

[0075] 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 plastic reduction and viscosity reduction liquefied waste plastic oil, the reaction temperature is 420°C, the residence time is 30 minutes, and the plastic reduction and viscosity reduction liquefied waste plastic oil is sent to a heating unit (heating furnace) for heating treatment to obtain heated liquefied waste plastic, the heating temperature is 480°C, the residence time is 60 minutes, and the steam injection amount in the heating furnace is 0.5% by weight; The heated liquefied waste plastic is sent to the pyrolysis reaction device. The top pressure of the pyrolysis tower is 0.2Mpa, the reaction temperature is 480℃, and the operation cycle is 2h (switching operation time of the pyrolysis tower) to obtain pyrolysis reaction products and coke.

[0076] The obtained pyrolysis reaction product was sent to an inertial separation unit (using the same cyclone separation device as in Example 1) for gas-solid separation treatment, and the separated pyrolysis reaction product was sent to a product separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. The product distribution test was carried out, and the distribution of the pyrolysis reaction products is shown in Table 2.

[0077] Example 3 A medium-sized device for continuous pyrolysis of waste plastics was used, with DCl-1 as raw material and a feed rate of about 5 kg / h. DCl-1 was fed into a screw heating and conveying equipment and further heated to 400°C for 12 min (liquefaction process); then the material was kept warm for plastic reduction, viscosity reduction and cracking treatment. The temperature for plastic reduction and viscosity reduction treatment was 380°C and the time for plastic reduction and viscosity reduction treatment was 1 h (using an adiabatic upflow plastic reduction and viscosity reduction reactor). When the outlet temperature of the heating furnace (reaction temperature) was 500°C and the pressure of the pyrolysis tower (reaction pressure) was 0.15 MPa, the distribution of RPCC processing products of waste agricultural film particles is shown in Table 3, the properties of the coke products are shown in Table 4, and the operation cycle is shown in Table 5.

[0078] Comparative Example 1 The process system, method and raw materials of Example 3 were used, except that no inertial separation unit was provided in the process system. The specific process conditions were the same as those of Example 3. The distribution of pyrolysis reaction products is shown in Table 4, and the operation cycle is shown in Table 5.

[0079] Comparative Example 2 The process system, method and raw materials of Example 3 are used. The reaction zone, necking zone and outlet zone are not set in the pyrolysis reaction device. The pyrolysis reaction device is only a conventional cylindrical reaction device, wherein the inner diameter of the reaction device is 500 mm, the outer diameter is 810 mm; the height of the reaction device is 2200 mm; the pressure in the reaction device is 0.15 MPa. The specific process conditions are the same as those of Example 3. The distribution of pyrolysis reaction products is shown in Table 4, and the operation cycle is shown in Table 5.

[0080] Example 4 The process system of Example 3 is used, the only difference being that the ratio of the inner diameter of the third equal-diameter cylinder to the inner diameter of the first equal-diameter cylinder is 0.25:1.

[0081] 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 6.

[0082] Example 5 The process system of Example 3 is adopted, the only difference being that the angle between the side wall of the second variable diameter cylinder and the axis of the pyrolysis reaction device is 8°.

[0083] 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 6.

[0084] Example 6 The process system of Example 3 is used, except that the ratio of the height of the third equal-diameter cylinder to the height of the first equal-diameter cylinder is 0.05:1; the ratio of the height of the second variable-diameter cylinder to the height of the first equal-diameter cylinder is 0.05:1; 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 6.

[0085] 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 0.05 MPa, the reaction temperature is 550°C, and the operation cycle is 2 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 7.

[0086] 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 0.02 MPa, the reaction temperature is 560°C, and the operation cycle is 1 h (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 7.

[0087] Table 1 Properties of waste agricultural film particles

[0088] Table 2 Distribution of pyrolysis reaction products of Example 1 and Example 2

[0089] Table 3 Distribution of pyrolysis products of Example 3, Comparative Example 1 and Comparative Example 2

[0090] Table 4 Properties of coke in Example 3, Comparative Example 1 and Comparative Example 2

[0091] Table 5 Distribution of pyrolysis reaction products

[0092] Table 6 Distribution of pyrolysis reaction products

[0093] As can be seen from Example 1, waste agricultural film is melt-dechlorinated by a twin-screw heating and conveying device to obtain dechlorinated waste plastic DCl-1. After de-plasticization and viscosity reduction at 400°C for 50 minutes, the sample flow state is stable. After being heated to 500°C, it is sent to the pyrolysis tower provided in Example 1 for pyrolysis reaction, and fractionated by a cyclone separator and a fractionating tower to obtain dry gas, liquefied gas, gasoline, diesel, wax oil and coke with yields of 6.54%, 11.78%, 29.32%, 28.57%, 21.16% and 2.31%, respectively, and the solid content in the wax oil fraction is only 0.01%. Since waste agricultural film 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.

[0094] As can be seen from Example 2, after the real waste plastic with high chlorine content is melt-dechlorinated by a twin-screw heating and conveying device, the sample has a stable flow state after plastic reduction and viscosity reduction at 420°C for 30 minutes. After being heated to 480°C, it enters the pyrolysis tower provided in Example 2 for pyrolysis reaction, and is fractionated by a cyclone separator and a fractionating tower to obtain dry gas, liquefied gas, gasoline, diesel, wax oil and coke with yields of 4.03%, 5.17%, 24.32%, 22.15%, 12.87% and 22.20%, respectively, and the solid content in the wax oil fraction is only 0.018%. 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.

[0095] It can be seen from Example 3 that after the waste agricultural film (particles) is processed by the process provided by the present invention, the liquid yield (including liquefied gas) of pyrolysis can reach 86.78%, the coke yield is relatively small, and the ash content of the coke is as high as 45.96% by weight. It cannot be sold as a product, but can be used as a boiler fuel for blending.

[0096] Comparing Example 3 with Comparative Examples 1 and 2, it can be seen that, combined with the data in Tables 3 and 4, the solid content in the wax oil fraction obtained by the gas-solid separation method provided by the present disclosure is lower, and the ash content in the coke product is lower.

[0097] 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 tower provided in Examples 4 to 6 is not within the scope of the present disclosure, the ash cannot be effectively separated separately, resulting in the solid content in the liquid product and the ash content in the coke product being higher than that in Example 3, and the total liquid yield is reduced.

[0098] By comparing Example 3 with Examples 7 and 8, it can be seen that, combined with the data in Table 6, since the pyrolysis reaction conditions in Examples 7 and 8 are not within the preferred range and limited range of the present disclosure, the solid content and coke content in the wax oil fraction in the pyrolysis reaction product are slightly increased compared with Example 3, and the liquid yield is lower than that of Example 3.

[0099] 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.

[0100] 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.

[0101] 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 treating waste plastics by reducing viscosity through thermal decomposition and cracking, 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 the waste plastic deplasticization and viscosity reduction unit for plastic deplasticization and viscosity reduction treatment to obtain liquefied waste plastic oil after plastic deplasticization and viscosity reduction; 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 a pyrolysis mixed product; S5, allowing the pyrolysis mixed product to enter an inertial separation unit for gas-solid separation treatment to obtain a pyrolysis product; S6, allowing the pyrolysis product to enter a product separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction; Wherein, the pyrolysis reaction unit comprises a pyrolysis reaction device, and along the material flow direction, the pyrolysis reaction device comprises a reaction zone, a necking zone and an outlet zone which are arranged in sequence.

2. The processing method according to claim 1, characterized in that: The shell of the pyrolysis reaction device 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 reaction zone, the second variable diameter cylinder forms the necking zone, and the third constant diameter cylinder forms the outlet 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 larger 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; wherein the diameter of the first constant diameter cylinder is larger than the 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 (0.01-0.2):1, preferably (0.01-0.15):1; further preferably, the inner diameter of the third equal-diameter cylinder is 5-800 mm, preferably 10-500 mm; the inner diameter of the first equal-diameter cylinder is 500-10000 mm, preferably 500-6000 mm; The ratio of the height of the second diameter-changing cylinder to the bottom cross-sectional diameter is (0.1-4.0):1, preferably (0.2-3.0):1; the angle between the side wall of the second diameter-changing cylinder and the axis of the pyrolysis reaction device is 10-80°, preferably 30-75°; The ratio of the height of the second variable diameter cylinder to the height of the first constant diameter cylinder is (0.1-0.8):1, preferably (0.1-0.5):1; 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 (0.1-0.5):

1.

3. 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 preliminary melting and liquefaction dechlorination unit for hot melt 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.

4. The processing method according to claim 3, 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.

5. 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 product separation unit to the waste 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 in the product separation unit is used as the wax oil fraction.

6. 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.; and a residence time of 1-20 min, preferably 1-15 min.

7. The processing method according to claim 3, characterized in that: The waste plastic preliminary melting, liquefaction and 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 hot 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 preliminary melting and liquefaction 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.

8. The processing method according to claim 1, characterized in that: In step S2, the waste plastics 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.

9. 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.

10. 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 450~520℃, preferably 480~520℃; the operation cycle of the pyrolysis tower is 1~500h, preferably 10~240h.

11. The processing method according to claim 1, characterized in that: In step S5, the inertial separation unit uses a cyclone separation device to perform gas-solid separation processing; The cyclone separation device comprises 1 to 4 groups of cyclone separator assemblies connected in parallel, and each group of cyclone separator assemblies comprises 1 to 3 stages of cyclone separators connected in series; The dust removal efficiency of the cyclone separation device is above 95%, and the pressure drop is below 1500Pa.

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 3-30% by weight.

13. A waste plastics viscosity reduction pyrolysis cracking treatment system, characterized in that: The treatment system includes: a waste plastic liquefaction unit, a waste plastic reduction and viscosity reduction unit, a material heating unit, a pyrolysis reaction unit, an inertial separation unit and a product 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 waste plastic deplasticization and viscosity reduction unit comprises a liquefied waste plastic inlet and a liquefied waste plastic oil outlet, and the plastic deplasticization and viscosity reduction unit is configured to perform plastic deplasticization 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, wherein the heating inlet is connected to the liquefied waste plastic oil outlet of the plastic reduction and viscosity reduction unit, and the material heating unit is configured to heat the liquefied waste plastic oil after plastic reduction and viscosity reduction. The pyrolysis reaction unit comprises a pyrolysis reaction device, and along the material flow direction, the pyrolysis reaction device comprises a reaction zone, a necking zone and an outlet zone arranged in sequence; The reaction zone, the necking zone and the outlet zone are axially distributed from bottom to top inside the pyrolysis reactor and are fluidically connected. The pyrolysis reaction unit includes a pyrolysis mixed reactant inlet and a pyrolysis mixed product outlet. The pyrolysis mixed reactant inlet is arranged at the bottom of the reaction zone, and the pyrolysis mixed product outlet is arranged at the top of the outlet zone. The pyrolysis mixed reactant inlet is connected to the heating outlet of the material heating unit. The pyrolysis reaction unit is configured to perform pyrolysis reaction treatment on the heated liquefied waste plastic; The inertial separation unit comprises a pyrolysis mixed product inlet, a solid outlet and a gas outlet, wherein the pyrolysis mixed product inlet is connected to the pyrolysis mixed product outlet of the pyrolysis reaction unit, and the inertial separation unit is configured to perform high-temperature gas-solid separation on the high-temperature pyrolysis product to remove solid particles; The product separation unit includes a product 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 product separation inlet is connected to the gas outlet of the inertial separation unit, and the product separation unit is configured to separate and process the pyrolysis products after gas-solid separation.

14. The processing system according to claim 13, characterized in that The shell of the pyrolysis reaction device 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 reaction zone, the second variable diameter cylinder forms the necking zone, and the third constant diameter cylinder forms the outlet 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 larger 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; wherein the diameter of the first constant diameter cylinder is larger than the 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 (0.01-0.2):1, preferably (0.01-0.15):1; further preferably, the inner diameter of the third equal-diameter cylinder is 5-800 mm, preferably 10-500 mm; the inner diameter of the first equal-diameter cylinder is 500-10000 mm, preferably 500-6000 mm; the ratio of the height of the second variable-diameter cylinder to the bottom cross-sectional diameter is (0.1-4.0) :1, preferably (0.2-3.0):1; the angle between the side wall of the second variable diameter cylinder and the axis of the pyrolysis reaction device is 10-80°, preferably 30-75°; the ratio of the height of the second variable diameter cylinder to the height of the first constant diameter cylinder is (0.1-0.8):1, preferably (0.1-0.5):1; the ratio of the height of the third constant diameter cylinder to the height of the first constant diameter cylinder is (0.1-1.0):1, preferably (0.1-0.5):1; The inertial separation unit uses a cyclone separation device to perform gas-solid separation processing; Preferably, the cyclone separation device comprises 1 to 4 groups of cyclone separator assemblies connected in parallel, and each group of cyclone separator assemblies comprises 1 to 3 stages of cyclone separators connected in series.

15. The processing system according to claim 13, characterized in that The system also includes a waste plastic preliminary melting, liquefaction and dechlorination unit and a hydrogen chloride absorption unit; The waste plastic preliminary melting and liquefaction dechlorination unit comprises a chlorine-containing waste plastic raw material inlet, a hydrogen chloride-containing gas phase material outlet and a dechlorinated waste plastic liquid phase material outlet, and the waste plastic preliminary melting and liquefaction dechlorination unit is configured to perform hot melt dechlorination treatment on the chlorine-containing waste plastic raw material; the dechlorinated waste plastic liquid phase material outlet is connected to the waste plastic to be treated inlet 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 preliminary melting and liquefaction dechlorination unit; Preferably, the waste plastic liquefaction includes a heating liquefaction conveying device; 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; Preferably, the waste plastic preliminary melting, liquefaction and 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 product separation unit; Optionally, the waste plastic preliminary melting, liquefaction and dechlorination unit further includes a non-condensable steam outlet.

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