Treatment method and treatment system for pyrolysis cracking of waste plastics

Abstract

The invention relates to a waste plastic pyrolysis cracking treatment method which comprises the following steps: enabling to-be-treated waste plastic to enter a waste plastic liquefaction unit for liquefaction treatment, and then feeding the to-be-treated waste plastic into 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 and dry gas; the plastic reduction and viscosity reduction unit comprises a plastic reduction and viscosity reduction reactor, a fluid distribution device is arranged in the plastic reduction and viscosity reduction reactor, and the fluid distribution device comprises a sieve plate distributor and an annular pipe distributor; an inlet of the sieve plate distributor is communicated with a liquefied waste plastic inlet of the plastic reduction and viscosity reduction reactor, and first distribution holes allowing liquefied waste plastic to circulate are formed in the sieve plate distributor; the annular pipe distributor is arranged in the circumferential direction of the side wall of the plastic reduction and viscosity reduction reactor, and second distribution holes allowing liquefied waste plastics to circulate are formed in the annular pipe distributor. According to the method, waste plastic resource utilization can be effectively achieved, and coke generation is reduced.

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 pyrolysis and cracking of waste plastic. Background Art

[0002] 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 recycle waste plastics quickly and greenly. The simplest chemical method for treating waste plastics is direct incineration, but direct incineration will produce toxic gases that are harmful to the human body and cause secondary environmental pollution. Waste plastic oil technology is to crack waste plastics under anaerobic or anoxic conditions by heating or with catalysts to crack polymers into low molecular weight substances to obtain gasoline, kerosene, diesel fractions and part of pyrolysis gas. On the one hand, waste plastic oil technology alleviates the pollution problem caused by waste plastics, and on the other hand, it realizes the recycling of waste plastics, which is an important direction for the resource treatment of waste plastics. Existing waste plastic oil recovery technologies mainly include 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. However, there are many problems in the waste plastic oil recycling technology. For example, the polyvinyl chloride in the waste plastic decomposes into HCl when heated, 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 the waste plastic. In addition, waste plastics are high molecular weight 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, resulting in a high pyrolysis coke rate and high gas yield of the waste plastic. At the same time, the density of waste plastics is low, and the rate at which waste plastics enter the reaction device is low. The processing scale of existing technologies is small and cannot meet the needs of modern large-scale recycling.

[0003] CN109401774A discloses a waste plastic continuous thermal cracking system and a thermal cracking method thereof, the system comprises a loading device, a feeding device, a thermal cracking reactor and a slag discharging device connected in sequence, and 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 subjected to uneven heating, and coking and fouling are easily generated. CN112538363A discloses a method for co-converting waste plastics in a delayed coker unit, the method converts waste plastics together with petroleum residual oil raw materials, and the waste plastics are selected from polyethylene, polypropylene, polystyrene, PET and multi-layer plastics with added metals, and also do not include waste plastics of polyvinyl chloride. Waste plastics form a high-viscosity polymer melt in the melting process, and there is a density difference problem with hydrocarbon raw materials, so the mixed fluid of hydrocarbons and polymer melts can cause problems such as blockage and coking of delayed coking heating furnace tubes. Summary of the invention

[0004] The purpose of the present disclosure is to provide a method and system for pyrolysis and cracking of waste plastics, which can effectively realize the resource-based, large-scale and continuous utilization of waste plastics and reduce the generation of coke.

[0005] In order to achieve the above-mentioned object, the present disclosure provides a first aspect of a method for treating waste plastic by 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 and dry gas; The plastic reduction and viscosity reduction unit comprises a plastic reduction and viscosity reduction reactor, wherein a fluid distribution device is arranged inside the plastic reduction and viscosity reduction reactor, and the fluid distribution device comprises a sieve plate distributor and a ring pipe distributor; The inlet of the sieve plate distributor is connected to the inlet of the liquefied waste plastic of the plastic reduction and viscosity reduction reactor, and the sieve plate distributor is provided with a first distribution hole allowing the liquefied waste plastic to flow; the ring pipe distributor is arranged circumferentially along the side wall of the plastic reduction and viscosity reduction reactor, and the ring pipe distributor is provided with a second distribution hole allowing the liquefied waste plastic to flow.

[0006] Optionally, the plastic reduction and viscosity reduction reactor further comprises a plurality of baffles; the baffles are arranged perpendicularly to the axial direction in the inner cavity of the plastic reduction and viscosity reduction reactor, the plurality of baffles are spaced apart and distributed along the axial direction, and the number of the baffles is 3 to 20; The sieve plate distributor, the ring pipe distributor and the partition are sequentially arranged in the inner cavity of the plastic reduction and viscosity reduction reactor from bottom to top along the axial direction; The top of the plastic reduction and viscosity reduction reactor is provided with a liquefied waste plastic oil outlet pipe.

[0007] Optionally, the distance between the sieve plate distributor and the ring tube distributor is 20-50 mm; The distance between the annular pipe distributor and the lowermost baffle is 300-800 mm; The distance between two adjacent partitions is 500-2000 mm; The distance between the uppermost baffle and the top of the plastic reduction and viscosity reduction reactor is 500-2000 mm.

[0008] Optionally, the cross-section of the plasticity reduction and viscosity reduction reactor is respectively circular; The cross-sectional diameter of the plastic reduction and viscosity reduction reactor is 400-3000 mm.

[0009] Optionally, the sieve plate distributor comprises a first inlet pipe, a variable diameter cylinder and a sieve plate which are sealed and connected in sequence from bottom to top, the diameter of the sieve plate is the same as the top cross-sectional diameter of the variable diameter cylinder, and the bottom cross-sectional diameter of the variable diameter cylinder is the same as the tube diameter of the first inlet pipe; the top cross-sectional diameter of the variable diameter cylinder is 300-2500 mm, and the bottom cross-sectional diameter of the variable diameter cylinder is 20-120 mm; The ratio of the height of the variable diameter cylinder to the bottom cross-sectional diameter is (1.2-5):1, and the angle between the side wall of the variable diameter cylinder and the axis of the plastic reduction and viscosity reduction reactor is 30-75°.

[0010] Optionally, the ring tube distributor comprises a ring tube and a second inlet tube, the ring tube is coaxially arranged inside the plastic reduction and viscosity reduction reactor, and the distance between the outer wall of the ring tube and the inner wall of the plastic reduction and viscosity reduction reactor is 5 to 20 mm.

[0011] Optionally, the lower end of the first inlet pipe extends to the outside of the plastic reduction and viscosity reduction reactor; The lower end of the second inlet pipe extends to the outside of the plastic reduction and viscosity reduction reactor; The lower end of the first inlet pipe is flush with the lower end of the second inlet pipe.

[0012] Optionally, the second distribution holes are toward the top of the plasticity reduction and viscosity reduction reactor; The diameter of the first distribution holes is 55-75 mm; the diameter of the second distribution holes is 7-15 mm; the diameter of the third distribution holes is 10-40 mm; The number of openings of the sieve plate of the sieve plate distributor is 20 to 50; the number of openings of the ring pipe of the ring pipe distributor is 10 to 30; and the number of openings of the partition is 20 to 50.

[0013] Optionally, the method further comprises: S3, allowing the liquefied waste plastic oil subjected to plastic reduction and visbreaking to enter a 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. The pyrolysis product enters a separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction.

[0014] Optionally, in step S1, the waste plastic liquefaction unit uses a heating and conveying device to perform the liquefaction process; optionally, the heating and conveying device includes a first screw-type heating and conveying device; preferably, the first screw-type heating and conveying device is selected from a twin-screw or single-screw heating and conveying device with heating; Preferably, the process conditions of the liquefaction treatment include: inlet temperature of 20-50°C, preferably 20-35°C; outlet temperature of 330-380°C, preferably 340-360°C; residence time of 1-20 min, preferably 5-15 min.

[0015] Optionally, in step S2, the operating linear speed of the plastic reduction and viscosity reduction reactor is 0.1 to 10 cm / s, preferably 0.15 to 5 cm / s; The linear velocity of the fluid at the inlet of the sieve plate distributor is 0.1-2.0 cm / s, preferably 0.1-1.0 cm / s, and the linear velocity of the fluid at the inlet of the ring pipe distributor is 1.0-20.0 cm / s, preferably 2.0-15 cm / s; The reaction temperature of the plastic reduction and viscosity reduction reactor is 370-450°C, preferably 380-420°C; the residence time of the plastic reduction and viscosity reduction reactor is 30-90min, preferably 30-70min; the bed pressure drop of the plastic reduction and viscosity reduction reactor is below 1000Pa, preferably below 800Pa.

[0016] Optionally, in step S3, the heating unit includes a heating furnace; Preferably, the process conditions of the heating treatment include: the outlet temperature of the heating furnace is 480-600° C., preferably 500-580° C.; optionally, the steam injection amount is 0.5-5% by weight, preferably 0.5-3% by weight.

[0017] 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.

[0018] Optionally, 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, wherein the wax oil fraction is sent to the plastic reduction and viscosity reduction reactor through the sieve plate distributor inlet and the ring pipe distributor inlet; the flow rate of the wax oil fraction flowing into the plastic reduction and viscosity reduction reactor through the sieve plate distributor inlet is 0.05~10.0m 3 / h, the flow rate of the wax oil fraction flowing into the plastic reduction and viscosity reduction reactor through the inlet of the annular pipe distributor is 0.01~2.0m 3 / h; Preferably, the weight ratio of the recycled wax oil fraction to the liquefied waste plastic 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 or the fraction with a distillation range of more than 350° C. in other processes is used as the wax oil fraction.

[0019] 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.

[0020] 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.

[0021] 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 the pulverization process is 100-2000 μm; 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.

[0022] A second aspect of the present disclosure provides a waste plastic pyrolysis and cracking treatment system, the treatment system comprising: a waste plastic liquefaction unit and a plastic reduction and viscosity reduction 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 plastic reduction and viscosity reduction reactor, wherein a fluid distribution device is arranged inside the plastic reduction and viscosity reduction reactor, wherein the fluid distribution device comprises a sieve plate distributor and a ring pipe distributor; the plastic reduction and viscosity reduction reactor, wherein a fluid distribution device is arranged inside the plastic reduction and viscosity reduction reactor, wherein the fluid distribution device comprises a sieve plate distributor and a ring pipe distributor; The inlet of the sieve plate distributor is connected to the inlet of the liquefied waste plastic of the plastic reduction and viscosity reduction reactor, and the sieve plate distributor is provided with a first distribution hole allowing the liquefied waste plastic to flow; the ring pipe distributor is arranged circumferentially along the side wall of the plastic reduction and viscosity reduction reactor, and the ring pipe distributor is provided with a second distribution hole allowing the liquefied waste plastic to flow.

[0023] Optionally, the plastic reduction and viscosity reduction reactor further includes a plurality of baffles; the baffles are arranged perpendicularly to the axial direction in the inner cavity of the plastic reduction and viscosity reduction reactor, the plurality of baffles are spaced and distributed along the axial direction, and the number of the baffles is 3 to 20; the sieve plate distributor, the ring pipe distributor and the baffles are sequentially arranged in the inner cavity of the plastic reduction and viscosity reduction reactor from bottom to top along the axial direction; the top of the plastic reduction and viscosity reduction reactor is provided with a liquefied waste plastic oil outlet pipe; The distance between the sieve plate distributor and the ring tube distributor is 20-50 mm; the distance between the ring tube distributor and the lowermost baffle is 300-800 mm; the distance between two adjacent baffles is 500-2000 mm; the distance between the uppermost baffle and the top of the plastic reduction and viscosity reduction reactor is 500-2000 mm; The cross-section of the plastic reduction and viscosity reduction reactor is respectively circular; the cross-section diameter of the plastic reduction and viscosity reduction reactor is 400-3000 mm; The sieve plate distributor comprises, from bottom to top, a sealed first inlet pipe, a variable diameter cylinder and a sieve plate, the diameter of the sieve plate is the same as the top cross-sectional diameter of the variable diameter cylinder, the bottom cross-sectional diameter of the variable diameter cylinder is the same as the tube diameter of the first inlet pipe; the top cross-sectional diameter of the variable diameter cylinder is 300-2500 mm, and the bottom cross-sectional diameter of the variable diameter cylinder is 20-120 mm; The ratio of the height of the variable diameter cylinder to the bottom cross-sectional diameter is (1.2-5): 1, and the angle between the side wall of the variable diameter cylinder and the axis of the plastic reduction and viscosity reduction reactor is 30-75°; The ring pipe distributor comprises a ring pipe and a second inlet pipe, the ring pipe is coaxially arranged inside the plastic reduction and viscosity reduction reactor, and the distance between the outer wall of the ring pipe and the inner wall of the plastic reduction and viscosity reduction reactor is 5-20 mm; The lower end of the first inlet pipe extends to the outside of the plastic reduction and viscosity reduction reactor; the lower end of the second inlet pipe extends to the outside of the plastic reduction and viscosity reduction reactor; the lower end of the first inlet pipe is flush with the lower end of the second inlet pipe; The second distribution hole is toward the top of the plastic reduction and viscosity reduction reactor; the hole diameter of the first distribution hole is 55-75 mm; the hole diameter of the second distribution hole is 7-15 mm; the hole diameter of the third distribution hole is 10-40 mm; the number of openings of the sieve plate of the sieve plate distributor is 20-50; the number of openings of the ring pipe of the ring pipe distributor is 10-30; the number of openings of the partition is 20-50; The plastic reduction and viscosity reduction reactor comprises a sieve plate distributor inlet, a ring pipe distributor inlet and a liquefied waste plastic oil outlet. The liquefied waste plastic outlet of the waste plastic liquefaction unit is respectively connected to the sieve plate distributor inlet and the ring pipe distributor inlet. The plastic reduction and viscosity reduction unit is configured to perform plastic reduction, viscosity reduction and cracking treatment on the liquefied waste plastic.

[0024] Optionally, the processing system further comprises: a heating unit, a pyrolysis reaction unit and a separation unit; The 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 heating unit is configured to heat the liquefied waste plastic oil after plastic reduction and viscosity reduction. The pyrolysis reaction unit comprises a pyrolysis reactant inlet and a pyrolysis product outlet, the pyrolysis reactant 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 high-temperature liquefied waste plastic; The separation unit comprises 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 pyrolysis product outlet of the pyrolysis reaction unit, and the wax oil fraction outlet is respectively connected to the sieve plate distributor inlet and the ring pipe distributor inlet, and the separation unit is configured to separate and process the pyrolysis products; 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 includes a heating and conveying device; optionally, the heating and conveying device includes a first screw-type heating and conveying device, and the first twin-screw heating and conveying device is connected to the sieve plate distributor inlet and the ring tube distributor inlet of the plastic reduction and viscosity reduction reactor; preferably, the first screw-type heating and conveying device is selected from a twin-screw or single-screw heating and 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 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 preliminary melting, liquefaction and dechlorination unit further includes a non-condensable steam outlet.

[0025] Through the above technical scheme, the present disclosure provides a treatment method and treatment system for pyrolysis and cracking of waste plastics. The present disclosure obtains liquefied waste plastics by rapidly liquefying the waste plastics to be treated, and sends the liquefied waste plastics into a plastic reduction and viscosity reduction reactor for plastic reduction and viscosity reduction cracking treatment. Since a fluid distribution device composed of a sieve plate distributor, a ring tube distributor and a partition is arranged inside the plastic reduction and viscosity reduction reactor, the fluid can enter the reactor evenly. On the one hand, the ring tube distributor can further increase the flow rate of the fluid at the wall surface, prevent back mixing caused by a slow flow rate at the wall surface, increase the convective heat transfer coefficient of the wall surface, and avoid On the other hand, the sieve plate distributor and the ring tube distributor act simultaneously to further increase the fluid flow rate inside the reactor, prevent the inclusion particles from settling at the bottom of the reactor, avoid reactor blockage, reduce the full-bed pressure drop of the reactor, and reduce the viscosity of the liquefied waste plastic without coking and excessive cracking, forming a uniform, fluid, and high-liquid thermally conductive fluidized waste plastic that can be transported by a pump; then it is treated by a heating furnace or other means to quickly reach the pyrolysis reaction temperature, and the heated liquefied waste plastic is transported to the pyrolysis tower for pyrolysis reaction, which can obtain a higher liquid yield and a lower coking rate. In addition, after the waste plastic is liquefied, the transport density of the raw material is greatly increased compared with that of solid waste plastic, so it can not only achieve large-scale processing of waste plastics, but also achieve continuous pyrolysis recovery of waste plastics.

[0026] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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 structural schematic diagram of the plastic reduction and viscosity reduction reactor provided in the present disclosure.

[0028] Figure 2 It is an exemplary structural schematic diagram of a sieve plate distributor, a ring pipe distributor and a partition plate inside the plastic reduction and viscosity reduction reactor provided by the present disclosure.

[0029] Figure 3 It is an exemplary flow chart of the treatment method and treatment system for pyrolysis and cracking of waste plastics provided in the present disclosure.

[0030] 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 outlet and gasoline fraction outlet, 15-dry gas outlet, 16-wax oil fraction outlet, 17-pipeline, 18-pipeline, 19-pipeline, 20-sieve plate distributor inlet, 21-ring pipe distributor inlet, 22-sieve plate distributor, 23-ring pipe distributor, 24-partition, 25-liquefied waste plastic oil outlet. DETAILED DESCRIPTION

[0031] 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.

[0032] The first aspect of the present disclosure provides a method for treating waste plastic by 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 and dry gas; The plastic reduction and viscosity reduction unit comprises a plastic reduction and viscosity reduction reactor 4, wherein a fluid distribution device is arranged inside the plastic reduction and viscosity reduction reactor 4, and the fluid distribution device comprises a sieve plate distributor 22 and a ring pipe distributor 23; The inlet of the sieve plate distributor 22 is connected to the inlet of the liquefied waste plastic of the plastic reduction and viscosity reduction reactor 4, and the sieve plate distributor 22 is provided with a first distribution hole allowing the liquefied waste plastic to flow; the ring pipe distributor 23 is arranged circumferentially along the side wall of the plastic reduction and viscosity reduction reactor 4, and the ring pipe distributor 23 is provided with a second distribution hole allowing the liquefied waste plastic to flow.

[0033] The present invention provides a method and system for treating waste plastic by thermal decomposition and cracking. The present invention obtains liquefied waste plastic by rapidly liquefying the waste plastic to be treated, and sends the liquefied waste plastic into a plastic reduction and viscosity reduction reactor for plastic reduction and viscosity reduction and cracking treatment. Since a fluid distribution device composed of a sieve plate distributor, a ring pipe distributor and a partition is arranged inside the plastic reduction and viscosity reduction reactor, the fluid can enter the reactor uniformly. On the one hand, the ring pipe distributor can further increase the fluid flow rate at the wall surface, prevent back mixing caused by a slow flow rate at the wall surface, increase the convective heat transfer coefficient of the wall surface, and avoid coking at the wall surface. On the other hand, the sieve plate distributor and the ring tube distributor act simultaneously to further increase the fluid flow rate inside the reactor, prevent the inclusion particles from settling at the bottom of the reactor, avoid reactor blockage, reduce the full-bed pressure drop of the reactor, and reduce the viscosity of the liquefied waste plastic without coking and excessive cracking, forming a uniform, fluid, and liquid fluidized waste plastic that can be transported by a pump. The waste plastic is then treated by a heating furnace or other means to quickly reach the pyrolysis reaction temperature, and the heated liquefied waste plastic is transported to the pyrolysis tower for pyrolysis reaction, which can obtain a higher liquid yield and a lower coking rate. In addition, after the waste plastic is liquefied, the transport density of the raw material is greatly increased compared to that of solid waste plastic, so it can not only achieve large-scale processing of waste plastics, but also achieve continuous pyrolysis recovery of waste plastics.

[0034] In a specific embodiment, the plastic reduction and viscosity reduction reactor further comprises a plurality of baffles; the baffles are arranged perpendicularly to the axial direction in the inner cavity of the plastic reduction and viscosity reduction reactor, the plurality of baffles are spaced apart along the axial direction, the number of the baffles is 3 to 20, preferably 5 to 10; the baffles are provided with third distribution holes for allowing the liquefied waste plastic to flow; The sieve plate distributor, the ring pipe distributor and the partition are sequentially arranged in the inner cavity of the plastic reduction and viscosity reduction reactor from bottom to top along the axial direction; The top of the plastic reduction and viscosity reduction reactor is provided with a liquefied waste plastic oil outlet pipe.

[0035] In the present disclosure, the plastic reduction and viscosity reduction reactor may include only one partition.

[0036] In the above embodiment, the partition is set in the plastic reduction and viscosity reduction reactor to effectively adjust the fluidity of the fluidized waste plastic, further increase the flow rate of the fluid inside the reactor, prevent the sedimentation of entrained particles at the bottom of the reactor, avoid reactor blockage, reduce the full-bed pressure drop of the reactor, and achieve the reduction of the viscosity of the liquefied waste plastic without coking and excessive cracking, thereby forming a uniform and fluid fluidized waste plastic that can be transported by a pump.

[0037] In a specific embodiment, the distance between the sieve plate distributor and the ring tube distributor is 20-50 mm, preferably 20-35 mm; The distance between the annular tube distributor and the lowermost baffle is 300-800 mm, preferably 400-700 mm; The distance between two adjacent partitions is 500-2000 mm, preferably 500-1500 mm; The distance between the uppermost baffle and the top of the plastic reduction and viscosity reduction reactor is 500-2000 mm, preferably 500-1500 mm.

[0038] In a specific embodiment, the cross section of the plastic reduction and viscosity reduction reactor is circular; Optionally, the diameter of the circular cross section of the plastic reduction and viscosity reduction reactor is 400-3000 mm, preferably 400-1500 mm.

[0039] In a specific embodiment, the sieve plate distributor comprises, from bottom to top, a sealed first inlet pipe, a variable diameter cylinder and a sieve plate, the diameter of the sieve plate is the same as the top cross-sectional diameter of the variable diameter cylinder, and the bottom cross-sectional diameter of the variable diameter cylinder is the same as the tube diameter of the first inlet pipe; the top cross-sectional diameter of the variable diameter cylinder is 300-2500 mm, preferably 300-1200 mm, and the bottom cross-sectional diameter of the variable diameter cylinder is 20-120 mm, preferably 20-100 mm; In a preferred embodiment, the ratio of the height of the variable diameter cylinder to the bottom cross-sectional diameter is (1.2~5):1, preferably (1.5~3):1, and the angle between the side wall of the variable diameter cylinder and the axis of the plastic reduction and viscosity reduction reactor is 30~75°, preferably 30~60°.

[0040] In a specific embodiment, the ring tube distributor includes a ring tube and a second inlet pipe, and the ring tube is sealed and connected to the second inlet pipe; the ring tube is coaxially arranged inside the plastic reduction and viscosity reduction reactor, and the distance between the outer wall of the ring tube and the inner wall of the plastic reduction and viscosity reduction reactor is 5~20mm, preferably 5~15mm.

[0041] In a specific embodiment, the lower end of the first inlet pipe extends to the outside of the plastic reduction and viscosity reduction reactor; The lower end of the second inlet pipe extends to the outside of the plastic reduction and viscosity reduction reactor; The lower end of the first inlet pipe of the ring is flush with the lower end of the second inlet pipe.

[0042] In a specific embodiment, the second distribution holes are oriented toward the top of the plasticity reduction and viscosity reduction reactor; The diameter of the first distribution holes is 55-75 mm, preferably 55-65 mm; the diameter of the second distribution holes is 7-15 mm, preferably 8-12 mm; the diameter of the third distribution holes is 10-40 mm, preferably 15-35 mm; The number of openings of the sieve plate of the sieve plate distributor is 20-50, preferably 20-40; the number of openings of the ring pipe of the ring pipe distributor is 10-30, preferably 10-25; the number of openings of the partition is 20-50, preferably 20-40.

[0043] In the above embodiment, the hole diameter and the number of openings of the distribution holes on the preferred sieve plate distributor, ring tube distributor and partition can make the fluid enter the interior of the reactor more evenly, further increase the fluid flow rate at the wall, prevent back mixing caused by slow flow rate at the wall, increase the convective heat transfer coefficient of the wall, and avoid coking at the wall; at the same time, increase the fluid flow rate inside the reactor, prevent organic particles from settling at the bottom of the reactor, avoid reactor clogging, reduce the pressure drop of the entire reactor bed, and achieve the reduction of the viscosity of the liquefied waste plastic without coking and excessive cracking, forming a uniform and fluid fluidized waste plastic that can be transported by a pump, realizing the resource utilization of waste plastics and reducing coke formation.

[0044] In a preferred embodiment, the method further comprises: S3, allowing the liquefied waste plastic oil subjected to plastic reduction and visbreaking to enter a 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. The pyrolysis product enters a separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction.

[0045] In the present disclosure, the liquefied waste plastics that have been deplasticized, viscous and cracked are heated to reach a pyrolysis reaction temperature and form a uniform, fluid logistics; the heated liquefied waste plastics are subjected to a pyrolysis reaction, thereby achieving resource utilization of the waste plastics and reducing coke generation.

[0046] 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.

[0047] In a preferred embodiment, the process conditions of the liquefaction treatment include: an inlet temperature of 20-50°C, preferably 20-35°C; an outlet temperature of 330-380°C, preferably 340-360°C; and a residence time of 1-20 min, preferably 5-15 min.

[0048] In one embodiment, in step S2, the operating linear speed of the plastic reduction and viscosity reduction reactor is 0.1 to 10 cm / s, preferably 0.15 to 5 cm / s; The linear velocity of the fluid at the inlet of the sieve plate distributor is 0.1-2.0 cm / s, preferably 0.1-1.0 cm / s, and the linear velocity of the fluid at the inlet of the ring pipe distributor is 1.0-20.0 cm / s, preferably 2.0-15.0 cm / s; The reaction temperature of the plastic reduction and viscosity reduction reactor is 370-450°C, preferably 380-420°C; the residence time of the plastic reduction and viscosity reduction reactor is 30-90min, preferably 30-70min; the bed pressure drop of the plastic reduction and viscosity reduction reactor is below 1000Pa, preferably below 800Pa.

[0049] In the above embodiment, the preferred operating linear velocity and fluid linear velocity can better control the fluid flow rate, make the fluid enter the reactor more evenly, prevent back mixing caused by slow flow rate at the wall, increase the convective heat transfer coefficient of the wall, and avoid coking at the wall; at the same time, the appropriate fluid flow rate can prevent the included particles from settling at the bottom of the reactor, avoid reactor blockage, and further reduce the full-bed pressure drop of the reactor.

[0050] In one embodiment, in step S3, the 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 480-600° C., preferably 500-580° C.; optionally, the steam injection amount is 0.5-5% by weight, preferably 0.5-3% by weight.

[0051] In one 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°C, preferably 480~550°C; the operation cycle of the pyrolysis tower is 1~500h, preferably 10~240h.

[0052] In the present disclosure, the pyrolysis reaction unit may include a plurality of pyrolysis towers arranged in parallel.

[0053] 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, wherein the wax oil fraction is sent to the plastic reduction and viscosity reduction reactor through the sieve plate distributor inlet and the ring pipe distributor inlet; the flow rate of the wax oil fraction flowing into the plastic reduction and viscosity reduction reactor through the sieve plate distributor inlet is 0.05~10.0m 3 / h, preferably 0.1~6.0m 3 / h, the flow rate of the wax oil fraction flowing into the plastic reduction and viscosity reduction reactor through the inlet of the annular pipe distributor is 0.01~2.0m 3 / h, preferably 0.02~1.0m 3 / h.

[0054] 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):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.

[0055] 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.

[0056] 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.

[0057] In the present disclosure, a dedicated device is used to quickly heat the 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] In one 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; In a preferred embodiment, 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.

[0062] In the present disclosure, the apparatus and method for cooling treatment and pulverizing treatment may be conventional apparatus and method in the art.

[0063] In one embodiment, the waste plastics to be processed include one or more of LDPE, HDPE, PS, PP, PET and PVC.

[0064] 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.

[0065] 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.

[0066] The second aspect of the present disclosure provides a waste plastic pyrolysis and cracking treatment system, such as Figure 1 As shown, the treatment system includes: a waste plastic liquefaction unit 3 and a plastic reduction and viscosity reduction unit 4; The waste plastic liquefaction unit 3 comprises an inlet for waste plastic to be processed and an outlet for liquefied waste plastic, and the waste plastic liquefaction unit 3 is configured to liquefy the waste plastic to be processed; like Figure 2 As shown, the plastic reduction and viscosity reduction unit includes a plastic reduction and viscosity reduction reactor 4, and a fluid distribution device is arranged inside the plastic reduction and viscosity reduction reactor 4, and the fluid distribution device includes a sieve plate distributor 22 and a ring pipe distributor 23; The inlet of the sieve plate distributor 22 is connected to the inlet of the liquefied waste plastic of the plastic reduction and viscosity reduction reactor 4, and the sieve plate distributor 22 is provided with a first distribution hole allowing the liquefied waste plastic to flow; the ring pipe distributor 23 is arranged circumferentially along the side wall of the plastic reduction and viscosity reduction reactor 4, and the ring pipe distributor 23 is provided with a second distribution hole allowing the liquefied waste plastic to flow.

[0067] In a specific implementation manner, Figure 2 As shown, the plastic reduction and viscosity reduction reactor 4 further includes a plurality of baffles 24; the baffles 24 are arranged perpendicularly to the axial direction in the inner cavity of the plastic reduction and viscosity reduction reactor, and the plurality of baffles are spaced and distributed along the axial direction, and the number of the baffles is 3 to 20, preferably 5 to 10; the baffles are provided with third distribution holes for allowing the liquefied waste plastic to flow; the sieve plate distributor 22, the annular tube distributor 23 and the baffles 24 are sequentially arranged in the inner cavity of the plastic reduction and viscosity reduction reactor 4 from bottom to top along the axial direction; the top of the plastic reduction and viscosity reduction reactor 4 is provided with a liquefied waste plastic oil outlet pipe 25; The distance between the sieve plate distributor 22 and the ring tube distributor 23 is 20-50 mm, preferably 20-35 mm; the distance between the ring tube distributor 23 and the lowermost baffle is 300-800 mm, preferably 400-700 mm; the distance between two adjacent baffles is 500-2000 mm, preferably 500-1500 mm; the distance between the uppermost baffle and the top of the plastic reduction and viscosity reduction reactor 4 is 500-2000 mm, preferably 500-1500 mm; The cross section of the plastic reduction and viscosity reduction reactor 4 is circular; optionally, the diameter of the circular cross section of the plastic reduction and viscosity reduction reactor 4 is 400-3000 mm, preferably 400-1500 mm; The sieve plate distributor 22 includes, from bottom to top, a sealed first inlet pipe, a variable diameter cylinder and a sieve plate, the diameter of the sieve plate is the same as the top cross-sectional diameter of the variable diameter cylinder, and the bottom cross-sectional diameter of the variable diameter cylinder is the same as the tube diameter of the first inlet pipe; the top cross-sectional diameter of the variable diameter cylinder is 300-2500mm, preferably 300-1200mm, and the bottom cross-sectional diameter of the variable diameter cylinder is 20-120mm, preferably 20-100mm; Preferably, the ratio of the height of the variable diameter cylinder to the bottom cross-sectional diameter is (1.2-5):1, preferably (1.5-3):1, and the angle between the side wall of the variable diameter cylinder and the axis of the plastic reduction and viscosity reduction reactor is 30-75°, preferably 30-60°; The ring pipe distributor 23 includes a ring pipe and a second inlet pipe, and the ring pipe is sealed and connected to the second inlet pipe; the ring pipe is coaxially arranged inside the plastic reduction and viscosity reduction reactor, and the distance between the outer wall of the ring pipe and the inner wall of the plastic reduction and viscosity reduction reactor is 5-20 mm, preferably 5-15 mm; The lower end of the first inlet pipe 20 extends to the outside of the plastic reduction and viscosity reduction reactor; the lower end of the second inlet pipe 21 extends to the outside of the plastic reduction and viscosity reduction reactor; the lower end of the first inlet pipe 20 is flush with the lower end of the second inlet pipe 21; The second distribution holes are toward the top of the plastic reduction and viscosity reduction reactor; the diameter of the first distribution holes is 55-75 mm, preferably 55-65 mm; the diameter of the second distribution holes is 7-15 mm, preferably 8-12 mm; the diameter of the third distribution holes is 10-40 mm, preferably 15-35 mm; the number of openings of the sieve plate of the sieve plate distributor is 20-50, preferably 20-40; the number of openings of the ring pipe of the ring pipe distributor is 10-30, preferably 10-25; the number of openings of the partition is 20-50, preferably 20-40; The plastic reduction and viscosity reduction reactor comprises a sieve plate distributor inlet, a ring pipe distributor inlet and a liquefied waste plastic oil outlet. The liquefied waste plastic outlet of the waste plastic liquefaction unit is respectively connected to the sieve plate distributor inlet and the ring pipe distributor inlet. The plastic reduction and viscosity reduction unit is configured to perform plastic reduction, viscosity reduction and cracking treatment on the liquefied waste plastic.

[0068] In one embodiment, the processing system further comprises: a heating unit 5, a pyrolysis reaction unit 6 and a separation unit 7; The heating unit 5 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 heating unit 5 is configured to heat the liquefied waste plastic oil after plastic reduction and viscosity reduction. The pyrolysis reaction unit 6 includes a pyrolysis reactant inlet and a pyrolysis product outlet, the pyrolysis reactant inlet is connected to the heating outlet of the heating unit, and the pyrolysis reaction unit 6 is configured to perform a pyrolysis reaction on the heated liquefied waste plastic; The separation unit 7 includes a separation inlet, a dry gas outlet 15, a liquefied gas outlet 14, a gasoline fraction outlet 14, a diesel fraction outlet 13 and a wax oil fraction outlet 16; the separation inlet is connected to the pyrolysis product outlet of the pyrolysis reaction unit, and the wax oil fraction outlet is respectively connected to the sieve plate distributor inlet and the ring pipe distributor inlet, and the separation unit is configured to separate and process the pyrolysis products.

[0069] In one embodiment, the separation unit may include a distillation device, a fractionation device and a rectification device.

[0070] In one embodiment, the system further comprises 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 includes a heating and conveying device; optionally, the heating and conveying device includes a first screw-type heating and conveying device, and the first twin-screw heating and conveying device is connected to the sieve plate distributor inlet and the ring pipe distributor inlet of the plastic reduction and viscosity reduction reactor; preferably, the first screw-type heating and conveying device is selected from a twin-screw heating and conveying device or a single-screw heating and conveying device with heating; preferably, the waste plastic melting and dechlorination unit includes a second screw-type heating and conveying device and a vacuum device connected to the second screw-type heating and conveying device; preferably, the second screw-type 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 viscosity reduction unit also includes a circulating oil inlet; the circulating oil inlet is connected to the wax oil fraction outlet of the separation unit; optionally, the waste plastic preliminary melting, liquefaction and dechlorination unit also includes a non-condensable steam outlet, and the non-condensable gas outlet is arranged at the top of the waste plastic melting and dechlorination unit.

[0071] The process flow of the system provided by the above specific embodiments in the present disclosure specifically includes: Figure 3 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, deairing and dechlorination, a gaseous material containing hydrogen chloride and a dechlorinated waste plastic material are obtained. The air and water vapor are first discharged from the pipeline 9 through the vacuum system, and then the gaseous material containing hydrogen chloride is pumped into the hydrogen chloride absorption unit 8 through the vacuum system to contact with the 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 the pipeline 19. The dechlorinated waste plastic liquid phase material from the melting dechlorination unit 2 can directly enter the waste plastic liquefaction unit 3. The waste plastic liquefaction unit adopts a first screw heating and conveying device. After extrusion and heating by the first screw heating and conveying device, molten liquefied waste plastic is obtained; the liquefied waste plastic is sent to the plastic reduction and viscosity reduction unit 4 through a pipeline. The plastic reduction and viscosity reduction unit adopts a plastic reduction and viscosity reduction reactor. The wax oil from the separation unit 7 and / or the wax oil of other processes are added into the plastic reduction and viscosity reduction reactor through the sieve plate distributor inlet 20 and the ring pipe distributor inlet 21 as the circulating oil inlet. After plastic reduction and viscosity reduction cracking, the plastic reduction and viscosity reduction liquefied waste plastic oil is obtained. The liquefied waste plastic oil with reduced plasticity and viscosity enters the pyrolysis reaction unit 6 through 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 the gas outlet 15, the liquefied gas and gasoline fractions exit the device from the liquefied gas and gasoline fraction outlet 14, and the diesel fraction exits the device from the diesel fraction outlet 13; the wax oil fraction at the bottom of the tower is led out of the separation unit through the wax oil fraction outlet 16, wherein part of the wax oil fraction can also be used as circulating oil to return to the plastic reduction and viscosity reduction unit 4 as a circulating oil inlet through the sieve plate distributor inlet 20 and the ring pipe distributor inlet 21 for recycling, and can also be used as a product leading device through pipeline 17.

[0072] The specific structure of the plastic reduction and viscosity reduction reactor provided by the above specific embodiments in the present disclosure includes: Figure 1 As shown: The plastic reduction and viscosity reduction reactor 4 adopts a bottom-in-top-out operation mode. After the preliminary liquefied waste plastic enters the reactor through the sieve plate distributor inlet 20 and the ring pipe distributor inlet 21, it evenly enters the reactor through the fluid distribution device to undergo plastic reduction, viscosity reduction and cracking treatment to obtain plastic reduction and viscosity reduction liquefied waste plastic oil and non-condensable gas.

[0073] 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.

[0074] Among them, the analysis method for chlorine content in liquefied waste plastics is: Q / SH 3360 270-2018.

[0075] 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.

[0076] The distribution of pyrolysis reaction products was obtained by simulated distillation NB / SH / T 0829-2010 method.

[0077] The density analysis method of gasoline, 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 gasoline, diesel, etc. is determined by chromatography analysis.

[0078] In the following examples, the particle size of the particles obtained by the pulverization process ranges from 100 to 2000 μm.

[0079] 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.

[0080] Among them, the plastic reduction and viscosity reduction unit 4 adopts a plastic reduction and viscosity reduction reactor, and a fluid distribution device is arranged inside the plastic reduction and viscosity reduction reactor, and the fluid distribution device includes a sieve plate distributor 22, a ring tube distributor 23 and 6 partitions 24. The sieve plate reactor 22 is placed in the middle of the plastic reduction and viscosity reduction reactor 4 perpendicular to the axial direction, and the ring tube reactor 23 is coaxially arranged inside the plastic reduction and viscosity reduction reactor 4. The distance between the outer wall of the ring tube and the inner side wall of the plastic reduction and viscosity reduction reactor is 8mm. The partition 24 is distributed at intervals along the axial direction, and the distance between two adjacent partitions is 645mm. The ring tube distributor is arranged above the sieve plate reactor with a spacing of 35mm. The distance between the ring tube distributor and the lowermost partition is 610mm, and the distance between the uppermost partition and the top of the plastic reduction and viscosity reduction reactor is 980mm. The diameter of the circular cross section of the plastic reduction and viscosity reduction reactor is 650mm. The sieve plate distributor includes a sieve plate, a variable diameter cylinder and a first inlet pipe. The diameter of the sieve plate is the same as the top cross-sectional diameter of the variable diameter cylinder, and the bottom cross-sectional diameter of the variable diameter cylinder is the same as the tube diameter of the inlet pipe; the top cross-sectional diameter of the variable diameter cylinder is 570mm, and the bottom cross-sectional diameter of the variable diameter cylinder is 100mm; the ratio of the height of the variable diameter cylinder to the bottom cross-sectional diameter is 2.0:1, and the angle between the side wall of the variable diameter cylinder and the axis of the plastic reduction and viscosity reduction reactor is 50°. 31 first distribution holes are provided on the sieve plate of the sieve plate distributor; 18 second distribution holes are provided on the ring tube of the ring tube distributor; 35 third distribution holes are provided on the partition plate; the hole diameter of the first distribution hole is 60mm; the hole diameter of the second distribution hole is 10mm; and the hole diameter of the third distribution hole is 30mm.

[0081] Waste agricultural film (mainly made of PE, with a chlorine content of 0.0162% by weight) was fed into the waste plastic melting dechlorination unit 2, which used a second twin-screw heating and conveying device, with a feed rate of about 100 kg / h, an outlet temperature of 220°C, a processing time of 6 min, a vacuum degree of 150 mmHg, a screw diameter of 65 mm, and an outlet pressure of 0.2 MPa. After melting dechlorination treatment, dechlorinated waste plastic WP-1 was obtained, and the properties of the obtained dechlorinated waste plastic WP-1 are shown in Table 1.

[0082] In the process of melting dechlorination, the gaseous material containing hydrogen chloride is extracted by a vacuum system and sent to the hydrogen chloride absorption unit 8 to contact with the hydrogen chloride absorbent (NaOH solution) for hydrogen chloride absorption treatment.

[0083] The dechlorinated waste plastic WP-1 is 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 is 360°C, the residence time is 6 minutes, the feed rate is 100 kg / h, the screw diameter of the first twin-screw heating and conveying equipment is 65 mm, and the outlet pressure of the first twin-screw heating and conveying equipment is 0.2 MPa.

[0084] The liquefied waste plastic is sent into the plastic reduction and viscosity reduction reactor 4 through the sieve plate distributor fluid inlet pipe 20 and the ring tube distributor inlet pipe 21. The operating linear velocity of the plastic reduction and viscosity reduction reactor is 0.20 cm / s, the fluid linear velocity at the sieve plate distributor inlet is 0.70 cm / s, the fluid linear velocity at the ring tube distributor inlet is 13.0 cm / s, the reaction temperature is 390°C, the residence time is 40 min, and the bed pressure drop is 280 Pa through computational fluid dynamics simulation calculation to obtain plastic reduction and viscosity reduction cracked liquefied waste plastic oil.

[0085] The deplasticized and viscosity-reduced liquefied waste plastic oil is sent to a heating unit (heating furnace) for heating to obtain heated liquefied waste plastic oil. The outlet temperature of the heating furnace is 500°C and the steam injection amount is 0.5% by weight. The heated liquefied waste plastic oil is then sent to a pyrolysis reaction unit (pyrolysis tower) for pyrolysis reaction under the conditions of a pressure of 0.2 MPa and a reaction temperature of 500°C. The operation cycle is 10 hours to obtain pyrolysis reaction products and coke.

[0086] The obtained pyrolysis reaction products enter the separation unit for separation to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction, and the product distribution test is carried out. The distribution of pyrolysis reaction products is shown in Tables 2 and 3.

[0087] Example 2 The plastic reduction and viscosity reduction unit adopts a plastic reduction and viscosity reduction reactor. Compared with the plastic reduction and viscosity reduction reactor used in Example 1, the only difference is that the distance between the outer wall of the ring tube and the inner wall of the plastic reduction and viscosity reduction reactor is 10 mm, the partitions are spaced apart along the axial direction, and the distance between two adjacent partitions is 720 mm. The ring tube distributor is arranged above the sieve plate reactor with a spacing of 40 mm. 42 first distribution holes are opened on the sieve plate of the sieve plate distributor; 25 second distribution holes are opened on the ring tube of the ring tube distributor; 48 third distribution holes are opened on the partition; the hole diameter of the first distribution hole is 75 mm; the hole diameter of the second distribution hole is 12 mm; the hole diameter of the third distribution hole is 35 mm.

[0088] Waste plastics (mainly PE and PU) are fed into the waste plastic melting dechlorination unit for melting dechlorination. The waste plastic melting dechlorination unit 2 uses a second twin-screw heating and conveying device, with a feed rate of about 100 kg / h, an outlet temperature of 300°C, a processing time of 5 min, a vacuum degree of 70 mmHg for the heating and conveying device, and the second twin-screw heating and conveying device is the same as that in Example 1. After melting dechlorination treatment, dechlorinated waste plastic WP-2 is obtained. The properties of the obtained dechlorinated waste plastic WP-2 are shown in Table 1. The absorption process of the hydrogen chloride-containing gas obtained by the dechlorination treatment of the twin-screw heating and conveying device is the same as that in Example 1.

[0089] The dechlorinated waste plastic WP-2 is 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 is 360°C, the residence time is 0.1h, and the feed rate is 100kg / h. The first twin-screw deheating and conveying equipment is the same as that in Example 1.

[0090] The liquefied waste plastics are sent into the plastic reduction and viscosity reduction reactor through the fluid inlet pipe of the sieve plate distributor and the inlet pipe of the ring tube distributor. The operating linear velocity of the plastic reduction and viscosity reduction reactor is 0.18 cm / s, the fluid linear velocity of the sieve plate distributor inlet is 0.85 cm / s, the fluid linear velocity of the ring tube distributor inlet is 11.2 cm / s, the reaction temperature is 380°C, the residence time is 60 min, and the bed pressure drop is 540 Pa through computational fluid dynamics simulation calculation.

[0091] The deplasticized and viscosity-reduced liquefied waste plastic oil is sent to a heating unit (heating furnace) for heating to obtain heated liquefied waste plastic oil. The outlet temperature of the heating furnace is 500°C and the steam injection amount is 0.5% by weight. The heated liquefied waste plastic oil is then sent to a pyrolysis reaction unit (pyrolysis tower) for pyrolysis reaction at a pressure of 0.2 MPa and a reaction temperature of 480°C. The operation cycle is 5 hours to obtain pyrolysis reaction products and coke.

[0092] The obtained pyrolysis reaction products were separated by a separation unit to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction, and the product distribution test was carried out. The distribution of pyrolysis reaction products is shown in Tables 2 and 3.

[0093] Example 3 The process system of Example 1 is used, the only difference being that no partition is provided inside the plastic reduction and viscosity reduction reactor.

[0094] Referring to the process flow of Example 1, the same waste plastic raw material WP-1 was used, and the specific process conditions were the same as those of Example 1. The distribution of pyrolysis reaction products is shown in Table 4.

[0095] Example 4 The process system of Example 1 is adopted, the only difference being that the sieve plate of the sieve plate distributor is provided with 10 first distribution holes; the ring pipe of the ring pipe distributor is provided with 5 second distribution holes; and the partition plate is provided with 10 third distribution holes.

[0096] Referring to the process flow of Example 1, the same waste plastic raw material WP-1 was used, and the specific process conditions were the same as those of Example 1. The distribution of pyrolysis reaction products is shown in Table 4.

[0097] Example 5 The process system of Example 1 is used, with the only difference being that the diameter of the first distribution holes is 32 mm; the diameter of the second distribution holes is 5 mm; and the diameter of the third distribution holes is 8 mm.

[0098] Referring to the process flow of Example 1, the same waste plastic raw material WP-1 was used, and the specific process conditions were the same as those of Example 1. The distribution of pyrolysis reaction products is shown in Table 4.

[0099] Example 6 A medium-sized device for continuous pyrolysis of waste plastics was used, WP-1 was used as raw material, and the feed rate was about 5kg / h. WP-1 was sent to a screw heating and conveying device for further heating to 340°C for 12 minutes (liquefaction process); then it entered the plastic reduction and viscosity reduction reactor for plastic reduction and viscosity reduction treatment. The plastic reduction and viscosity reduction treatment conditions were the same as those in Example 1. The liquefied waste plastic oil obtained by plastic reduction and viscosity reduction was sent to a heating unit (heating furnace) for heating to obtain heated liquefied waste plastic oil. The outlet temperature (reaction temperature) of the heating furnace was 500°C, the pressure (reaction pressure) of the pyrolysis tower was 0.15MPa, the distribution of RPCC processing products of waste agricultural film particles (dry ash-free treatment) was shown in Table 5, the distribution of gas phase products was shown in Table 8, the liquid product was cut to obtain naphtha, diesel and wax oil components, and their properties were shown in Table 9, and the properties of the coke product were shown in Table 10.

[0100] Example 7 The waste plastic melting dechlorination unit includes a screw heating and conveying device and a vacuum device connected to the screw heating and conveying device. The screw heating and conveying device adopts a twin-screw heating and conveying device with a screw diameter of 55mm and an outlet pressure of 0.2MPa. 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.

[0101] Waste plastics (made of PE, PP, PS, PVC, etc., with a chlorine content of about 9% by weight) were fed into a screw heating and conveying device for hot melt dechlorination treatment to obtain dry gas containing hydrogen chloride and dechlorinated waste plastic materials. The feed rate of the twin-screw heating and conveying device was about 100 kg / h, and different outlet temperatures were set at 260°C, 300°C, 320°C, and 360°C. The reaction time was 6 minutes, and the vacuum degree of the vacuum device was 150 mmHg. The morphology and chlorine content of the waste plastics after transportation were tested under different outlet temperature conditions, and waste plastic samples WP-7-260, WP-7-300, WP-7-320, and WP-7-360 were obtained respectively. The properties of the obtained liquefied dechlorinated waste plastics are shown in Table 6.

[0102] Example 8 The method, process system and raw material WP-1 of Example 1 are used, except that the operating linear speed of the plastic reduction and viscosity reduction reactor is 5 cm / s. The fluid linear velocity at the inlet of the sieve plate distributor is 1.5 cm / s, the fluid linear velocity at the inlet of the ring tube distributor is 15.0 cm / s, the reaction temperature is 400°C, the residence time is 40 min, and the bed pressure drop is 1472 Pa through computational fluid dynamics simulation calculation. The distribution of pyrolysis reaction products is shown in Table 7.

[0103] Example 9 The method, process system and raw material WP-1 of Example 1 are used, except that the operating linear velocity of the plastic reduction and viscosity reduction reactor is 0.30 cm / s. The fluid linear velocity at the inlet of the sieve plate distributor is 0.07 cm / s, the fluid linear velocity at the inlet of the ring tube distributor is 20 cm / s, the reaction temperature is 390°C, the residence time is 40 min, and the bed pressure drop is 1425 Pa through computational fluid dynamics simulation calculation. The distribution of pyrolysis reaction products is shown in Table 7.

[0104] Comparative Example 1 The process system, method and raw materials of Example 6 are used, except that the waste plastic raw material WP-1 is not subjected to liquefaction treatment and plastic reduction and visbreaking treatment, but is directly introduced into an autoclave for heating, and the reaction temperature is set to 500°C and the residence time is 2h. Then a pyrolysis reaction is carried out to obtain pyrolysis products and coke, and the pyrolysis products enter a separation unit for separation to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. The specific process conditions are the same as those of Example 6. The distribution of pyrolysis reaction products is shown in Table 5.

[0105] Comparative Example 2 The process system, method and raw materials of Example 6 are used, with the only difference being that no fluid distribution device and internal components are provided inside the plastic reduction and viscosity reduction reactor.

[0106] The dechlorinated waste plastic WP-1 in Example 6 was used as a raw material, and a twin-screw heating and conveying device was used for liquefaction treatment to obtain liquefied waste plastic. The feed rate was about 5kg / h, the outlet temperature of the liquefied waste plastic was 380°C, and the residence time was 6min. Then, it was kept warm in an adiabatic upflow visbreaking reactor and subjected to visbreaking treatment. The reaction temperature was 380°C and the residence time was 1h. The operating linear velocity of the plastic-reducing and visbreaking reactor was 0.20cm / s. The bed pressure drop was 1350Pa through computational fluid dynamics simulation calculation. The material after plastic-reducing and visbreaking was sent to a heating unit (heating furnace) for heating treatment, and the outlet temperature of the heating furnace was 520°C. The heated waste plastic oil obtained was sent to a pyrolysis reaction device (pyrolysis tower) for pyrolysis reaction to obtain pyrolysis products and coke; the pyrolysis products were separated in a fractionating tower. The pressure of the pyrolysis tower was 0.15MPa, the reaction temperature of the pyrolysis tower was 520°C, the operation cycle was 6h, and the distribution of pyrolysis reaction products was shown in Table 5.

[0107] Comparative Example 3 The process system of Example 6 is used, the only difference being that no sieve plate distributor and no ring pipe distributor are provided inside the plastic reduction and viscosity reduction reactor, and the interior of the plastic reduction and viscosity reduction reactor only includes 6 partitions.

[0108] Referring to the process flow of Example 6, the same waste plastic raw material WP-1 was used, and the specific process conditions were the same as those of Example 6. The distribution of pyrolysis reaction products is shown in Table 5.

[0109] Table 1 Properties of waste plastics after dechlorination

[0110] Table 2 Distribution of waste plastic pyrolysis products

[0111] Table 3 Mass composition of dry gas and liquefied gas produced by pyrolysis of waste plastics

[0112] Table 4 Distribution of waste plastic pyrolysis products

[0113] Table 5 Distribution of waste plastic pyrolysis products

[0114] Table 6 Properties of dechlorinated waste plastics under different temperature conditions in Example 7

[0115] Table 7 Distribution of waste plastic pyrolysis products

[0116] Table 8 Gas composition of waste plastic pyrolysis products

[0117] Table 9 Properties of liquid products in the pyrolysis reaction of waste plastics

[0118] Table 10 Properties of coke in the pyrolysis products of waste plastics

[0119] As can be seen from Example 1, the waste agricultural film is subjected to a melting dechlorination process by a twin-screw heating and conveying device to obtain the dechlorinated waste plastic WP-1, and the dechlorinated waste plastic WP-1 is subjected to plastic reduction and viscosity reduction by the plastic reduction and viscosity reduction reactor provided in Example 1, and then heated to 500°C and enters the pyrolysis tower, and is fractionated by the fractionation tower to obtain dry gas, liquefied gas, gasoline, diesel, wax oil and coke with yields of 3.18%, 9.89%, 33.88%, 21.53%, 13.79% and 9.0%. 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 the treated waste plastic, so the chlorine content of WP-1 remains unchanged.

[0120] As can be seen from Example 2, the waste plastics are melted and dechlorinated by a twin-screw heating and conveying device to obtain dechlorinated waste plastics WP-2, and the dechlorinated waste plastics WP-2 are de-plasticized and de-viscosified by the de-plasticizing and de-viscosifying reactor provided in Example 2, and then heated to 500°C before entering a pyrolysis tower, and fractionated by a fractionation tower to obtain dry gas, liquefied gas, gasoline, diesel, wax oil, and coke with yields of 8.05%, 9.46%, 15.40%, 28.66%, 15.69%, and 15.75%. Since the waste plastics contain a certain amount of polyester, and after long-term oxidation, the raw materials contain a certain amount of oxygen, so the pyrolysis products contain a certain amount of CO2.

[0121] It can be seen from Examples 3 to 5 that when no partition is provided in the plasticity reduction and viscosity reduction reactor and the number of openings and the hole diameter of the distributor in the reactor are not within the specified range of the present disclosure, the flow rate of the fluid entering the reactor is uneven, which can easily cause coking and excessive cracking problems. The coke content in the obtained pyrolysis reaction product is slightly higher than that in Example 1, and the liquid yield is reduced.

[0122] As can be seen from Example 6, after the waste agricultural film (particles) is processed by the process provided by the present disclosure, the liquid yield (including liquefied gas) of pyrolysis can reach 85.84%, and the yield of coke and ash is relatively small. From the properties of the obtained gasoline, diesel and wax oil, it can be seen that the hydrogen mass fraction of each distillate oil is high, the olefin mass fraction is high, the aromatic mass fraction is low, and the chlorine and silicon heteroatom content is low, and it can be directly sent to the refinery for post-processing. The sum of the triene mass fractions in the pyrolysis gas is high (>45% by weight), and the ash content of the coke is as high as 51.64% by weight, which cannot be sold as a product, but can be used as a boiler fuel for blending.

[0123] It can be seen from Example 7 that as the outlet temperature of the second twin-screw pyrolysis and conveying equipment increases, the chlorine content in the waste plastics continues to decrease. When the dechlorination outlet temperature is greater than 300°C during the melting and dechlorination process of the waste plastics, the dechlorination rate of the obtained liquefied dechlorinated waste plastics is relatively high.

[0124] By comparing Example 6 with Comparative Examples 1 to 3, it can be seen from Comparative Example 1 that the same raw materials as those in Example 6 cannot form uniform, fluidized waste plastics with good fluidity that can be transported by a pump because they have not been liquefied and plasticized, resulting in the inability to achieve high-density continuous feeding. On the other hand, the use of a kettle reactor for heating treatment and pyrolysis reaction results in a small intermittent reaction processing capacity, and since solid plastics are poor conductors of heat, heat transfer is slow and uneven, which can easily cause local excessive cracking. Therefore, compared with Example 6, in Comparative Example 1, the yields of dry gas, liquefied gas, gasoline and coke increase, the yields of diesel and wax oil decrease, and the total liquid yield also decreases. It can be seen from Comparative Example 2 that the same raw materials as in Example 6, due to the fact that no fluid distribution device and internal components are set inside the plastic reduction and viscosity reduction reactor, the particles are seriously deposited in the plastic reduction and viscosity reduction reactor, so that the coke yield in the pyrolysis reaction product is lower than that in Example 6, but at the same time, the total liquid yield will be reduced compared with Example 6; on the other hand, the bed pressure drop of the plastic reduction and viscosity reduction reactor in Comparative Example 2 is relatively high, and the particles are deposited at the bottom of the reactor, which is easy to cause blockage and even shutdown. It can be seen from Comparative Example 3 that since only 6 baffles are set inside the plastic reduction and viscosity reduction reactor, the flow rate of the fluid entering the reactor is uneven, which is easy to cause coking and excessive cracking problems, thereby increasing the yields of dry gas, liquefied gas, gasoline and coke in the pyrolysis reaction product, and the diesel yield, wax oil yield and total liquid yield are reduced compared with Example 6.

[0125] As can be seen from Table 7, by comparing Example 8 with Example 1, it can be seen that when the operating linear velocity of the plastic reduction and viscosity reduction reactor and the fluid linear velocity of the sieve plate distributor are not within the preferred range of the present disclosure, the fluid flow rate cannot be well controlled, the fluid cannot enter the reactor uniformly, and it is easy to cause coking and excessive cracking problems, and the yields of dry gas, gasoline and coke in the pyrolysis reaction product are slightly increased, and the diesel yield, wax oil yield and total liquid yield are slightly lower than those in Example 1. Comparing Example 9 with Example 1, it can be seen that when the operating linear velocity of the plastic reduction and viscosity reduction reactor, the fluid linear velocity of the sieve plate distributor and the fluid linear velocity of the ring tube distributor are all not within the specified range of the present disclosure, the flow rate of the fluid entering the reactor will also be uneven, so that the yields of dry gas, gasoline and coke in the pyrolysis reaction product are slightly increased, and the diesel yield, wax oil yield and total liquid yield are slightly lower than those in Example 1.

[0126] 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.

[0127] 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.

[0128] 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 pyrolysis 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 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 and dry gas; The plastic reduction and viscosity reduction unit comprises a plastic reduction and viscosity reduction reactor (4), a fluid distribution device is arranged inside the plastic reduction and viscosity reduction reactor (4), and the fluid distribution device comprises a sieve plate distributor (22) and a ring pipe distributor (23); The inlet of the sieve plate distributor (22) is connected to the inlet of the liquefied waste plastic of the plastic reduction and viscosity reduction reactor (4), and the sieve plate distributor (22) is provided with first distribution holes that allow the liquefied waste plastic to flow; the ring tube distributor (23) is arranged along the circumference of the side wall of the plastic reduction and viscosity reduction reactor (4), and the ring tube distributor (23) is provided with second distribution holes that allow the liquefied waste plastic to flow.

2. The processing method according to claim 1, characterized in that: The plastic reduction and viscosity reduction reactor further comprises a plurality of baffles; the baffles are arranged perpendicularly to the axial direction in the inner cavity of the plastic reduction and viscosity reduction reactor, the plurality of baffles are spaced and distributed along the axial direction, and the number of the baffles is 3 to 20; the baffles are provided with third distribution holes for allowing the liquefied waste plastic to flow; The sieve plate distributor, the ring pipe distributor and the partition are sequentially arranged in the inner cavity of the plastic reduction and viscosity reduction reactor from bottom to top along the axial direction; The top of the plastic reduction and viscosity reduction reactor is provided with a liquefied waste plastic oil outlet pipe.

3. The processing method according to claim 2, characterized in that: The distance between the sieve plate distributor and the ring tube distributor is 20-50 mm; The distance between the annular pipe distributor and the lowermost baffle is 300-800 mm; The distance between two adjacent partitions is 500-2000 mm; The distance between the uppermost partition and the top of the plastic reduction and viscosity reduction reactor is 500-2000 mm.

4. The processing method according to claim 1, characterized in that: The cross section of the plastic reduction and viscosity reduction reactor is circular; Optionally, the diameter of the circular cross-section of the plastic reduction and viscosity reduction reactor is 400-3000 mm.

5. The processing method according to claim 1, characterized in that: The sieve plate distributor comprises a first inlet pipe, a variable diameter cylinder and a sieve plate which are sealed and connected in sequence from bottom to top, the diameter of the sieve plate is the same as the top cross-sectional diameter of the variable diameter cylinder, and the bottom cross-sectional diameter of the variable diameter cylinder is the same as the tube diameter of the first inlet pipe; the top cross-sectional diameter of the variable diameter cylinder is 300-2500 mm, and the bottom cross-sectional diameter of the variable diameter cylinder is 20-120 mm; Preferably, the ratio of the height of the variable diameter cylinder to the bottom cross-sectional diameter is (1.2-5):1, and the angle between the side wall of the variable diameter cylinder and the axis of the plasticity reduction and viscosity reduction reactor is 30-75°.

6. The processing method according to claim 1, characterized in that: The ring tube distributor comprises a ring tube and a second inlet tube, and the ring tube is sealed and connected to the second inlet tube; the ring tube is coaxially arranged inside the plastic reduction and viscosity reduction reactor, and the distance between the outer wall of the ring tube and the inner wall of the plastic reduction and viscosity reduction reactor is 5-20 mm.

7. The processing method according to claim 5 or 6, characterized in that: The lower end of the first inlet pipe extends to the outside of the plastic reduction and viscosity reduction reactor; The lower end of the second inlet pipe extends to the outside of the plastic reduction and viscosity reduction reactor; The lower end of the first inlet pipe is flush with the lower end of the second inlet pipe.

8. The processing method according to claim 2, characterized in that: The second distribution holes are oriented toward the top of the plasticity reduction and viscosity reduction reactor; The diameter of the first distribution holes is 55-75 mm; the diameter of the second distribution holes is 7-15 mm; the diameter of the third distribution holes is 10-40 mm; The number of openings of the sieve plate of the sieve plate distributor is 20 to 50; the number of openings of the ring pipe of the ring pipe distributor is 10 to 30; and the number of openings of the partition is 20 to 50.

9. The processing method according to claim 1, characterized in that: The method further includes: S3, allowing the liquefied waste plastic oil subjected to plastic reduction and visbreaking to enter a 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. The pyrolysis product enters a separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction.

10. The processing method according to claim 1, characterized in that: In step S1, the waste plastic liquefaction unit uses a heating and conveying device to perform the liquefaction process; optionally, the heating and conveying device includes a first screw-type heating and conveying device; preferably, the first screw-type heating and conveying device is selected from a twin-screw heating and conveying device with heating or a single-screw heating and conveying device; Preferably, the process conditions of the liquefaction treatment include: inlet temperature of 20-50°C, preferably 20-35°C; outlet temperature of 330-380°C, preferably 340-360°C; residence time of 1-20 min, preferably 5-15 min.

11. The processing method according to claim 1, characterized in that: In step S2, the operating linear speed of the plastic reduction and viscosity reduction reactor is 0.1 to 10 cm / s, preferably 0.15 to 5 cm / s; The linear velocity of the fluid at the inlet of the sieve plate distributor is 0.1-2.0 cm / s, preferably 0.1-1.0 cm / s, and the linear velocity of the fluid at the inlet of the ring pipe distributor is 1.0-20.0 cm / s, preferably 2.0-15 cm / s; The reaction temperature of the plastic reduction and viscosity reduction reactor is 370-450°C, preferably 380-420°C; the residence time of the plastic reduction and viscosity reduction reactor is 30-90min, preferably 30-70min; the bed pressure drop of the plastic reduction and viscosity reduction reactor is below 1000Pa, preferably below 800Pa.

12. The processing method according to claim 9, characterized in that: In step S3, the heating unit includes a heating furnace; Preferably, the process conditions of the heating treatment include: the outlet temperature of the heating furnace is 480-600° C., preferably 500-580° C.; optionally, the steam injection amount is 0.5-5% by weight, preferably 0.5-3% by weight.

13. The processing method according to claim 9, 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.

14. The processing method according to claim 9, characterized in that: The method further includes: At least part of the wax oil fraction from the separation unit is returned to the plastic reduction and viscosity reduction unit for recycling, wherein the wax oil fraction is sent to the plastic reduction and viscosity reduction reactor through the sieve plate distributor inlet and the ring pipe distributor inlet; the flow rate of the wax oil fraction flowing into the plastic reduction and viscosity reduction reactor through the sieve plate distributor inlet is 0.05~10.0m 3 / h, the flow rate of the wax oil fraction flowing into the plastic reduction and viscosity reduction reactor through the inlet of the annular pipe distributor is 0.01~2.0m 3 / h; Preferably, the weight ratio of the recycled wax oil fraction to the liquefied waste plastic 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 or the fraction with a distillation range of more than 350° C. in other processes is used as the wax oil fraction.

15. 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; 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.

16. The processing method according to claim 15, 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.

17. The processing method according to claim 15, 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 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 the pulverization process is 100-2000 μm; 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.

18. A waste plastic pyrolysis and cracking treatment system, characterized in that: The treatment system includes: a waste plastic liquefaction unit and a plastic reduction and viscosity reduction 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 plastic reduction and viscosity reduction reactor, wherein a fluid distribution device is arranged inside the plastic reduction and viscosity reduction reactor, wherein the fluid distribution device comprises a sieve plate distributor and a ring pipe distributor; a plastic reduction and viscosity reduction reactor (4), wherein a fluid distribution device is arranged inside the plastic reduction and viscosity reduction reactor (4), wherein the fluid distribution device comprises a sieve plate distributor (22) and a ring pipe distributor (23); The inlet of the sieve plate distributor (22) is connected to the inlet of the liquefied waste plastic of the plastic reduction and viscosity reduction reactor (4), and the sieve plate distributor (22) is provided with first distribution holes that allow the liquefied waste plastic to flow; the ring tube distributor (23) is arranged along the circumference of the side wall of the plastic reduction and viscosity reduction reactor (4), and the ring tube distributor (23) is provided with second distribution holes that allow the liquefied waste plastic to flow.

19. The processing system according to claim 18, characterized in that The plastic reduction and viscosity reduction reactor (4) further comprises a plurality of partitions (24); the partitions (24) are arranged perpendicularly to the axial direction in the inner cavity of the plastic reduction and viscosity reduction reactor, the plurality of partitions are spaced apart along the axial direction, and the number of the partitions is 3 to 20; the partitions are provided with third distribution holes for allowing the liquefied waste plastic to flow; the sieve plate distributor (22), the ring pipe distributor (23) and the partitions (24) are arranged in sequence from bottom to top in the inner cavity of the plastic reduction and viscosity reduction reactor along the axial direction; The top of the plastic reduction and viscosity reduction reactor is provided with a liquefied waste plastic oil outlet pipe; The distance between the sieve plate distributor and the ring tube distributor is 20-50 mm; the distance between the ring tube distributor and the lowermost baffle is 300-800 mm; the distance between two adjacent baffles is 500-2000 mm; the distance between the uppermost baffle and the top of the plastic reduction and viscosity reduction reactor is 500-2000 mm; The cross section of the plastic reduction and viscosity reduction reactor is circular; the diameter of the circular cross section of the plastic reduction and viscosity reduction reactor is 400-3000 mm; The sieve plate distributor comprises, from bottom to top, a sealed first inlet pipe, a variable diameter cylinder and a sieve plate, the diameter of the sieve plate is the same as the top cross-sectional diameter of the variable diameter cylinder, the bottom cross-sectional diameter of the variable diameter cylinder is the same as the tube diameter of the first inlet pipe; the top cross-sectional diameter of the variable diameter cylinder is 300-2500 mm, and the bottom cross-sectional diameter of the variable diameter cylinder is 20-120 mm; The ratio of the height of the variable diameter cylinder to the bottom cross-sectional diameter is (1.2-5): 1, and the angle between the side wall of the variable diameter cylinder and the axis of the plastic reduction and viscosity reduction reactor is 30-75°; The ring pipe distributor comprises a ring pipe and a second inlet pipe, the ring pipe is coaxially arranged inside the plastic reduction and viscosity reduction reactor, and the distance between the outer wall of the ring pipe and the inner wall of the plastic reduction and viscosity reduction reactor is 5-20 mm; The lower end of the first inlet pipe extends to the outside of the plastic reduction and viscosity reduction reactor; the lower end of the second inlet pipe extends to the outside of the plastic reduction and viscosity reduction reactor; the lower end of the first inlet pipe is flush with the lower end of the second inlet pipe; The second distribution hole is toward the top of the plastic reduction and viscosity reduction reactor; the hole diameter of the first distribution hole is 55-75 mm; the hole diameter of the second distribution hole is 7-15 mm; the hole diameter of the third distribution hole is 10-40 mm; the number of openings of the sieve plate of the sieve plate distributor is 20-50; the number of openings of the ring pipe of the ring pipe distributor is 10-30; the number of openings of the partition is 20-50; The plastic reduction and viscosity reduction reactor comprises a sieve plate distributor inlet, a ring pipe distributor inlet and a liquefied waste plastic oil outlet. The liquefied waste plastic outlet of the waste plastic liquefaction unit is respectively connected to the sieve plate distributor inlet and the ring pipe distributor inlet. The plastic reduction and viscosity reduction unit is configured to perform plastic reduction, viscosity reduction and cracking treatment on the liquefied waste plastic.

20. The processing system according to claim 18, characterized in that The processing system also includes: a heating unit, a pyrolysis reaction unit and a separation unit; The 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 heating unit is configured to heat the liquefied waste plastic oil after plastic reduction and viscosity reduction. The pyrolysis reaction unit comprises a pyrolysis reactant inlet and a pyrolysis product outlet, the pyrolysis reactant inlet is connected to the heating outlet of the heating unit, and the pyrolysis reaction unit is configured to perform a pyrolysis reaction on the heated liquefied waste plastic; The separation unit comprises 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 pyrolysis product outlet of the pyrolysis reaction unit, and the wax oil fraction outlet is respectively connected to the sieve plate distributor inlet and the ring pipe distributor inlet, and the separation unit is configured to separate and process the pyrolysis products; 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 includes a heating and conveying device; optionally, the heating and conveying device includes a first screw-type heating and conveying device, and the first twin-screw heating and conveying device is connected to the sieve plate distributor inlet and the ring tube distributor inlet of the plastic reduction and viscosity reduction reactor; preferably, the first screw-type heating and conveying device is selected from a twin-screw heating and conveying device with heating or a single-screw heating and 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 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 preliminary melting, liquefaction and dechlorination unit also includes a non-condensable steam outlet.

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