Processing method and processing system for plastic reduction, pyrolysis and catalytic cracking of waste plastics

Abstract

The invention relates to a processing method for plastic reduction, pyrolysis and catalytic cracking of waste plastics. The method comprises the following steps: sequentially feeding the waste plastics to be treated into a waste plastic liquefaction unit and a waste plastic visbreaking unit for liquefaction treatment and visbreaking treatment; the obtained visbreaking liquefied waste plastic oil is fed into a material heating unit to be heated, and heated liquefied waste plastics and first dry gas are obtained; the heated liquefied waste plastic oil enters a pyrolytic reaction unit to be subjected to a pyrolytic reaction, and pyrolysis product oil gas and coke are obtained; feeding the pyrolysis product oil gas into a catalytic cracking reaction unit, and contacting the pyrolysis product oil gas with a fluidized contact agent for cracking reaction to obtain reaction oil gas and a spent contact agent; and enabling the reaction oil gas to enter a separation unit for separation treatment to obtain second dry gas, liquefied gas, a gasoline fraction, a diesel fraction and a wax oil fraction. According to the present invention, the high yield of low-carbon olefin or aromatic hydrocarbon under the catalytic cracking reaction of the contact agents with different properties can be achieved so as to achieve the large-scale, continuous and green resource utilization of the waste plastic.

Description

Technical Field

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

[0002] At present, waste plastic oil recovery technology mainly includes waste plastic thermal cracking, catalytic thermal cracking and thermal cracking catalytic modification technology. The thermal cracking method has the advantages of simple process, relatively less equipment investment, no need for catalyst, and short reaction process. CN109401774A discloses a waste plastic continuous thermal cracking system and a thermal cracking method thereof, which includes a feeding device, a feeding device, a thermal cracking reactor and a slag discharge device connected in sequence. Since the plastic is a macromolecular polymer, a non-Newtonian fluid is formed during the heating process, and a screw propeller is used. The plastic liquefaction process in this process is unevenly heated, and coking and fouling are easily generated. CN112608761A provides a solid heat carrier internal heat type waste plastic treatment process, which solves the problem that the existing waste plastic treatment process is difficult to scale up and has low thermal efficiency by using iron ore pellets as a heat carrier to heat waste plastics. However, there is no dechlorination means in this process, which makes the impurity content in the pyrolysis oil too high. CN106118707A discloses a device and method for harmless treatment of waste plastics, wherein a large screw feeding device heats the waste plastics to 100-250°C and enters a dechlorination diverter for dechlorination reaction. Since the dechlorination reaction of PVC and the addition reaction of olefins are carried out simultaneously, the dechlorination rate is not high under the condition of separating HCl without external force; and the waste plastics are only softened into a plastic polymer material at 250°C, and its physical phase is a non-self-flowing non-liquid plastic solid, which is difficult to output from the dechlorination diverter. In addition, for catalytic cracking processes, the existing technologies are mainly focused on one-stage catalytic cracking, hydrocracking, and research on catalysts. However, most of these technologies directly feed solid raw materials into the reactor, and there are problems such as small processing capacity.

[0003] Most of the existing waste plastic oil recovery technologies have the following technical problems: 1. 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 plastic's exterior to be overheated and cracked, while the interior of the plastic remains solid, resulting in a high pyrolysis coke rate and high gas yield for waste plastics. At the same time, polyvinyl chloride in waste plastics is decomposed 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 waste plastics. On the other hand, 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. Summary of the invention

[0004] The purpose of the present invention is to provide a processing method and system for the plasticity reduction pyrolysis and catalytic cracking of waste plastics, which can achieve the production of more low-carbon olefins or more aromatics under the catalytic cracking reaction of contact agents of different properties, so as to realize large-scale, continuous and green resource utilization of waste plastics.

[0005] In order to achieve the above-mentioned object, the present disclosure provides a first aspect of a processing method for waste plastics by pyrolysis and catalytic 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 waste plastic viscosity reducing unit for visbreaking treatment to obtain visbreaking liquefied waste plastic oil; S3, allowing the visbroken liquefied waste plastic oil to enter a material heating unit for heating treatment to obtain high-temperature liquefied waste plastic and a first dry gas; S4, allowing the high-temperature liquefied waste plastic oil to enter a pyrolysis reaction unit for pyrolysis reaction to obtain pyrolysis products of oil gas and coke; S5, allowing the pyrolysis product oil and gas to enter a catalytic cracking reaction unit, contact with a fluidized contact agent to perform a cracking reaction, and obtain reaction oil and gas and a contact agent to be produced; S6. Allow the reaction oil and gas to enter a separation unit for separation treatment to obtain a second dry gas, liquefied gas, a gasoline fraction, a diesel fraction and a wax oil fraction.

[0006] Optionally, the method further comprises: returning at least part of the wax oil fraction obtained in step S6 to the catalytic cracking reaction unit to continue the cracking reaction; Preferably, the weight ratio of the returned wax oil fraction to the pyrolysis product wax oil is (0.1~1):1.

[0007] Optionally, before step S1, the method further includes: The chlorine-containing waste plastic raw material enters the waste plastic preliminary melting and liquefaction dechlorination unit for hot melt dechlorination treatment to obtain a gas phase material containing hydrogen chloride and a dechlorinated waste plastic material; allowing the dechlorinated waste plastic material to enter the waste plastic liquefaction unit; or The dechlorinated waste plastic material is subjected to cooling treatment and crushing treatment in sequence to obtain dechlorinated waste plastic particles; and the dechlorinated waste plastic particles are allowed to enter the waste plastic liquefaction unit.

[0008] 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.

[0009] Optionally, the method further comprises: the catalytic cracking reaction unit in step S3 performs cracking reaction to obtain charcoal ash; The method further comprises: allowing the ash with carbon and the contact agent to be regenerated to enter a regeneration unit, and in the presence of oxygen, allowing the contact agent to be regenerated and the carbon on the ash with carbon to undergo a complete combustion reaction to obtain regenerated flue gas and regenerated contact agent; Preferably, the method further comprises: Allow at least a portion of the first dry gas and / or at least a portion of the second dry gas to enter the regeneration unit, so that the regenerated contact agent and the ash with carbon undergo a complete combustion reaction in the presence of oxygen and dry gas to obtain regenerated flue gas and regenerated contact agent; Preferably, based on the total weight of the contact agent to be regenerated, the carbon content of the contact agent to be regenerated is 0.5-5.0 wt %.

[0010] Optionally, in step S1, the waste plastic liquefaction unit uses a rapid heating liquefaction conveying device to perform the liquefaction treatment; optionally, the rapid heating liquefaction conveying device includes a first screw-type heating conveying device; preferably, the first screw-type heating conveying device is selected from a twin-screw or single-screw heating conveying device with heating; Preferably, the process conditions of the liquefaction treatment include: an outlet temperature of 370-500° C., preferably 380-450° C.; and a residence time of 5-20 min, preferably 5-15 min.

[0011] Optionally, in step S2, the waste plastic viscosity reduction unit uses a viscosity reduction reactor to perform the viscosity reduction and cracking treatment; preferably, the viscosity reduction reactor is an adiabatic viscosity reduction reactor; Preferably, the process conditions of the visbreaking treatment include: a reaction temperature of 370-450° C., preferably 380-420° C., more preferably 390-420° C.; and a residence time of 2-120 min, preferably 30-70 min.

[0012] Optionally, in step S3, the material heating unit includes a heating furnace; Preferably, the process conditions of the heating treatment include: the outlet temperature of the heating furnace is 450°C~550°C, preferably 460°C~520°C, the residence time is less than 60s, preferably 30~50s; optionally, the steam injection amount is 0.5~5% by weight, optimized to 1~3% by weight.

[0013] Optionally, in step S4, the process conditions of the pyrolysis reaction include: the top pressure of the pyrolysis tower is 0.05~0.6MPa, preferably 0.1~0.3Mpa; the pyrolysis reaction temperature is 450~520℃, preferably 480~520℃; the pyrolysis tower operation cycle is 1~72h, preferably 8~24h.

[0014] Optionally, in step S5, the process conditions of the cracking reaction include: a reaction temperature of 490-750°C, a weight hourly space velocity of 1-100h -1 , the mass ratio of the contact agent to the waste plastic to be treated is (5~30):1; Preferably, the reaction temperature is 500-650°C and the weight hourly space velocity is 3-60h -1 , the mass ratio of the contact agent to the waste plastic to be treated is (6~20):1; Preferably, the visbroken liquefied waste plastic oil and steam are allowed to enter the contact cracking reaction unit; preferably, the mass ratio of steam to the waste plastic to be treated is (0-1):1, preferably (0.05-0.5):1.

[0015] Optionally, in step S5, the contact agent is one or more selected from silicon-aluminum material catalyst, quartz sand or coal coke powder; preferably, the particle size of the contact agent is 20-3000 μm; Optionally, the silicon-aluminum material is selected from a catalyst containing a molecular sieve and / or a catalyst not containing a molecular sieve; preferably, the catalyst containing a molecular sieve is a catalyst containing one or more molecular sieves selected from X molecular sieve, Y molecular sieve, mordenite, ZSM-5, pillared clay molecular sieve, SAPO, and one or more waste FCC catalysts; Preferably, the catalyst not containing molecular sieve is selected from a catalyst prepared with one or more of the first raw materials as raw materials, wherein the first raw material includes amorphous silica-alumina, clay, kaolin, montmorillonite, rectorite, illite, chlorite, pseudo-boehmite and silicon dioxide; or The catalyst not containing molecular sieve is selected from catalysts prepared with one or more of the second raw materials treated by acid washing, calcination and sieving as raw materials, wherein the second raw materials include amorphous silica-alumina, clay, kaolin, montmorillonite, rectorite, illite and chlorite; or selected from catalysts prepared with one or more of the second raw materials treated by acid washing, calcination and sieving and pseudo-boehmite and / or silicon dioxide as raw materials; Optionally, the coal tar powder is coal powder and / or petroleum coke powder.

[0016] Optionally, the regeneration treatment is carried out in a dense fluidized bed regenerator; preferably, the process conditions of the regeneration treatment include: air residence time of 0.5~60 seconds, preferably 1.0~10 seconds, the gasification temperature of the dense bed is 600~750°C, preferably 600~700°C, the gas introduced is a gas containing 10~50 volume % oxygen, and the linear velocity of the dense bed is 0.05~0.6m / s, preferably 0.2~0.4m / s.

[0017] Optionally, the waste plastic preliminary melting, liquefaction and dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw or single-screw conveying device; Preferably, the process conditions of the hot melt dechlorination treatment include: a feed rate of 5 to 5000 kg / h, preferably 100 to 4000 kg / h; an outlet temperature of 150 to 370°C, preferably 300 to 330°C, a reaction time of 0.1 to 0.5 h, preferably 0.1 to 0.3 h; a vacuum degree of the waste plastic preliminary melting and liquefaction dechlorination unit of 50 to 300 mmHg, preferably 50 to 150 mmHg; Preferably, the particle size of the dechlorinated waste plastic particles obtained by pulverization is 100-2000 μm.

[0018] Optionally, the waste plastics to be processed include one or more of LDPE, HDPE, PS, PP, PET and PVC; Optionally, the chlorine content in the waste plastic to be processed is less than 10% by weight; the ash content in the waste plastic to be processed is 1-40% by weight, preferably 3-30% by weight.

[0019] The second aspect of the present disclosure provides a processing system for plastic reduction pyrolysis and catalytic cracking of waste plastics, the processing system comprising: a waste plastic liquefaction unit, a waste plastic viscosity reduction unit, a material heating unit, a pyrolysis reaction unit, a catalytic cracking reaction unit and a separation unit; The waste plastic liquefaction unit comprises an inlet for waste plastic to be processed and an outlet for liquefied waste plastic, and the waste plastic liquefaction unit is configured to liquefy the waste plastic to be processed; The waste plastic viscosity reduction unit comprises a liquefied waste plastic inlet, a liquefied waste plastic oil outlet and a first dry gas outlet, and the waste plastic viscosity reduction unit is configured to perform viscosity reduction and cracking treatment on the liquefied waste plastic; The material heating unit comprises a heating inlet and a heating outlet, wherein the heating inlet is connected to the liquefied waste plastic oil outlet of the waste plastic viscosity reduction unit, and the material heating unit is configured to heat the liquefied waste plastic oil after viscosity reduction and cracking; The pyrolysis reaction unit has a pyrolysis reactant inlet and a pyrolysis product outlet, the pyrolysis reactant inlet is connected to the heating outlet of the material heating unit, and the pyrolysis reaction unit is configured to perform pyrolysis reaction treatment on high-temperature liquefied waste plastics; The catalytic cracking reaction unit comprises a cracking feed inlet, a contact agent inlet, a reaction oil and gas outlet and a regenerated contact agent outlet; the cracking feed inlet is connected to the pyrolysis product outlet of the pyrolysis reaction unit, and the contact cracking reaction unit is configured to perform a cracking reaction on the waste plastic pyrolysis reaction oil and gas; The separation unit includes a separation inlet, a second dry gas outlet, a liquefied gas outlet, a gasoline fraction outlet, a diesel fraction outlet and a wax oil fraction outlet; the separation inlet is connected to the reaction oil and gas outlet of the catalytic cracking unit, and the separation unit is configured to separate the reaction oil and gas.

[0020] Optionally, the system further comprises a regeneration unit, a waste plastic preliminary melting, liquefaction and dechlorination unit and a hydrogen chloride absorption unit; The regeneration unit comprises a regenerated contact agent inlet, an oxygen-containing gas inlet, a regenerated contact agent outlet and a regenerated flue gas outlet; the regeneration unit is configured to regenerate the regenerated contact agent in the presence of oxygen to obtain a regenerated contact agent and a regenerated flue gas; the regenerated contact agent outlet is connected to the contact agent inlet of the catalytic cracking reaction unit; The regeneration unit further comprises a dry gas inlet, which is connected to the first dry gas outlet of the waste plastic viscosity reduction unit and / or the second dry gas outlet of the separation unit; The waste plastic preliminary melting, liquefaction and dechlorination unit comprises a chlorine-containing waste plastic raw material inlet, a hydrogen chloride-containing gas phase material outlet and a dechlorinated waste plastic liquid phase material outlet, and the waste plastic preliminary melting, liquefaction and dechlorination unit is configured to perform melting and dechlorination treatment on the chlorine-containing waste plastic raw material; the dechlorinated waste plastic liquid phase material outlet is connected to the waste plastic to be treated inlet of the waste plastic liquefaction unit; The hydrogen chloride absorption unit comprises a hydrogen chloride-containing gas phase material inlet, a hydrogen chloride absorbent and a dechlorination dry gas outlet; the hydrogen chloride-containing gas phase material inlet is connected to the hydrogen chloride-containing gas phase material outlet of the waste plastic preliminary melting and liquefaction dechlorination unit; Preferably, the waste plastic liquefaction unit comprises a heating liquefaction conveying device; optionally, the heating liquefaction conveying device comprises a first screw-type heating conveying device; preferably, the first screw-type heating conveying device is selected from a twin-screw or single-screw heating conveying device with heating; Preferably, the waste plastic preliminary melting, liquefaction and dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw or single-screw conveying device; Preferably, the waste plastic 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.

[0021] Through the above technical scheme, the present invention provides a processing method and processing system for rapid liquefaction and pyrolysis cracking of waste plastics. The present invention obtains viscous and cracked liquefied waste plastic oil by rapidly liquefying and visbreaking the waste plastics to be processed, thereby reducing the viscosity of the liquefied waste plastics without coking and excessive cracking, improving the transportation density of the raw materials, and forming fluidized waste plastics that can be transported by a pump, which is uniform, has good fluidity, and has high liquid thermal conductivity; then, the liquefied waste plastics are treated by a heating furnace or the like to quickly reach the pyrolysis reaction temperature, and the heated liquefied waste plastics are transported to a pyrolysis tower for pyrolysis reaction. The pyrolysis products do not need to be separated, and all directly enter the contact cracking reactor in a gas phase, thereby reducing the amount of steam used, and can produce more low-carbon olefins or more aromatics under the catalytic cracking reaction of contact agents of different properties, so as to obtain a higher liquid yield and a lower coking rate, so as to achieve large-scale, continuous, and green resource utilization of waste plastics.

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

[0023] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings: Figure 1 It is an exemplary flow chart of a processing method and a processing system for the plasticity reduction, pyrolysis and catalytic cracking of waste plastics provided in the present disclosure.

[0024] Description of Reference Numerals 1-waste plastic storage tank, 2-waste plastic preliminary melting, liquefaction and dechlorination unit, 3-rapid heating and liquefaction transportation equipment, 4-waste plastic viscosity reduction unit, 5-heating furnace, 6-pyrolysis reaction unit, 7-catalytic cracking reaction unit, 8-regeneration unit, 9-separation unit, 10-hydrogen chloride absorption unit, 11-pipeline, 12-pipeline, 13-pipeline, 14-pipeline, 15-pipeline, 16-pipeline, 17-pipeline, 18-pipeline, 19-pipeline, 20-pipeline, 21-pipeline, 22-pipeline, 23-pipeline, 24-pipeline, 25-pipeline. DETAILED DESCRIPTION

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

[0026] The first aspect of the present disclosure provides a method for processing waste plastics by pyrolysis and catalytic cracking, such as Figure 1 As shown, 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 waste plastic viscosity reducing unit for visbreaking treatment to obtain visbreaking liquefied waste plastic oil; S3, allowing the visbroken liquefied waste plastic oil to enter a material heating unit for heating treatment to obtain heated liquefied waste plastic and a first dry gas; S4, allowing the heated liquefied waste plastic oil to enter a pyrolysis reaction unit for pyrolysis reaction to obtain pyrolysis products of oil gas and coke; S5, allowing the pyrolysis product oil and gas to enter a catalytic cracking reaction unit, contact with a fluidized contact agent to perform a cracking reaction, and obtain reaction oil and gas and a contact agent to be produced; S6. Allow the reaction oil and gas to enter a separation unit for separation treatment to obtain a second dry gas, liquefied gas, a gasoline fraction, a diesel fraction and a wax oil fraction.

[0027] The present invention provides a processing method and system for rapid liquefaction and pyrolysis cracking of waste plastics. The present invention obtains viscous and cracked liquefied waste plastic oil by rapidly liquefying and visbreaking the waste plastics to be processed, thereby reducing the viscosity of the liquefied waste plastics without coking and over-cracking, improving the delivery density of the raw materials, and forming fluidized waste plastics that are uniform, have good fluidity, and have high liquid thermal conductivity and can be delivered by a pump; then, the liquefied waste plastics are treated by a heating furnace or the like to quickly reach the pyrolysis reaction temperature, and the heated liquefied waste plastics are delivered to a pyrolysis tower for pyrolysis reaction. The pyrolysis products do not need to be separated, and all directly enter the contact cracking reactor in a gas phase, thereby reducing the amount of steam used, and can produce more low-carbon olefins or more aromatics under the catalytic cracking reaction of contact agents of different properties, thereby obtaining a higher liquid yield and a lower coking rate, and realizing large-scale, continuous, and green resource utilization of waste plastics.

[0028] In a specific embodiment, the method further comprises: returning at least part of the wax oil fraction obtained in step S6 to the catalytic cracking reaction unit to continue the cracking reaction; Preferably, the weight ratio of the returned wax oil fraction to the pyrolysis product wax oil is (0.1~1):1.

[0029] Processing according to the above-mentioned implementation method can further improve the utilization efficiency of waste plastic resources; and the introduction of wax oil fraction into the catalytic cracking reaction unit is also beneficial to the cracking reaction of waste plastics.

[0030] In a preferred embodiment, before step S1, the method further comprises: The chlorine-containing waste plastic raw material enters the waste plastic preliminary melting and liquefaction dechlorination unit for hot melt dechlorination treatment to obtain a gas phase material containing hydrogen chloride and a dechlorinated waste plastic material; Allowing the dechlorinated waste plastic material to enter the waste plastic liquefaction unit; or, The dechlorinated waste plastic material is subjected to cooling treatment and crushing treatment in sequence to obtain dechlorinated waste plastic particles; and the dechlorinated waste plastic particles are allowed to enter the waste plastic liquefaction unit.

[0031] 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.

[0032] In the present disclosure, a dedicated device is used to quickly heat polyvinyl chloride to decompose it, and a vacuum method is used to quickly separate the decomposed HCl from the reactor to improve the dechlorination efficiency.

[0033] 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; 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.

[0034] 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.

[0035] In a preferred embodiment, Figure 1 As shown, the method further comprises: in step S3, the catalytic cracking reaction unit performs cracking reaction to obtain charcoal ash; In a specific embodiment, the method further comprises: allowing the ash with carbon and the regenerated contact agent to enter a regeneration unit for regeneration treatment, and in the presence of oxygen, allowing the regenerated contact agent and the carbon on the ash with carbon to undergo a complete combustion reaction to obtain regenerated flue gas and regenerated contact agent. The processing method provided by the present disclosure can regenerate the regenerated contact agent containing carbon by a complete combustion reaction, thereby realizing the recycling of the contact agent.

[0036] In a preferred embodiment, Figure 1 As shown, the method also includes: Allow at least a portion of the first dry gas and / or at least a portion of the second dry gas to enter the regeneration unit for regeneration treatment, so that the regenerated contact agent and the ash with carbon undergo a complete combustion reaction in the presence of oxygen and dry gas to obtain regenerated flue gas and regenerated contact agent; Preferably, based on the total weight of the contact agent to be regenerated, the carbon content of the contact agent to be regenerated is 0.5-5.0 wt %.

[0037] The present invention uses dry gas generated in the waste plastic processing process to regenerate the contact agent to be recycled, thereby improving resource utilization efficiency and contact agent regeneration efficiency.

[0038] In a specific implementation, when the regeneration flue gas reaches the emission standard, the regeneration flue gas is discharged; wherein the regeneration flue gas emission standard is a conventional standard in the art, for example, referring to GB13271-2014 standard.

[0039] In one embodiment, in step S1, the waste plastic liquefaction unit uses a rapid heating liquefaction conveying device to perform the liquefaction treatment; optionally, the rapid heating liquefaction 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 with heating or a single-screw heating conveying device; In a preferred embodiment, the process conditions of the liquefaction treatment include: an outlet temperature of 370-500° C., preferably 380-450° C.; and a residence time of 1-20 min, preferably 1-15 min.

[0040] In one embodiment, in step S2, the waste plastic viscosity reduction unit uses a viscosity reduction reactor to perform the visbreaking treatment; preferably, the viscosity reduction reactor is an adiabatic viscosity reduction reactor. In the present disclosure, the adiabatic viscosity reduction reactor can be any reactor known in the art, such as an upflow viscosity reduction reactor or a downflow viscosity reduction reactor.

[0041] In a preferred embodiment, the process conditions of the visbreaking treatment include: a reaction temperature of 370-450°C, preferably 380-420°C, and more preferably 390-420°C; and a residence time of 2-120 min, preferably 30-70 min. According to the preferred visbreaking process conditions in this embodiment, a better viscosity reduction effect can be obtained.

[0042] In one embodiment, in step S3, the material heating unit includes a heating furnace; In a preferred embodiment, the process conditions of the heat treatment include: the outlet temperature of the heating furnace is 450°C~550°C, preferably 460°C~520°C, the residence time is less than 60s, preferably 30~50s; optionally, the steam injection amount is 0.5~5% by weight, optimized to 1~3% by weight.

[0043] 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 450~520℃, preferably 480~520℃; the pyrolysis tower operation cycle is 1~72h, preferably 8~24h.

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

[0045] In one embodiment, in step S5, the process conditions of the cracking reaction include: a reaction temperature of 490-750°C, a weight hourly space velocity of 1-100h -1 , the mass ratio of the contact agent to the waste plastic to be treated is (5-30): 1. In the present disclosure, the cracking reaction is carried out in a fluidized bed reactor, and the fluidized bed reactor is a conventional structure in the art.

[0046] In a preferred embodiment, in step S3, the process conditions of the cracking reaction include: a reaction temperature of 500-650°C, a weight hourly space velocity of 3-60h -1 , the mass ratio of the contact agent to the waste plastic to be treated is (6-20): 1. Carrying out the cracking reaction according to the process conditions of this embodiment can obtain a better cracking product distribution.

[0047] In a preferred embodiment, the method further comprises: allowing the visbroken liquefied waste plastic oil and steam to enter the contact cracking reaction unit; preferably, the mass ratio of steam to the waste plastic to be treated is (0-1):1, preferably (0.05-0.5):1.

[0048] In one embodiment, in step S5, the contact agent is one or more selected from silicon-aluminum material catalyst, quartz sand or coal coke powder; preferably, the particle size of the contact agent is 20-3000 μm; Optionally, the silicon-aluminum material is selected from a catalyst containing molecular sieves and / or a catalyst not containing molecular sieves; preferably, the catalyst containing molecular sieves is a catalyst containing one or more molecular sieves selected from X molecular sieve, Y molecular sieve, mordenite, ZSM-5, pillared clay molecular sieve and SAPO and / or a spent FCC catalyst; Preferably, the catalyst not containing molecular sieve is selected from a catalyst prepared with one or more of the first raw materials as raw materials, wherein the first raw material includes amorphous silica-alumina, clay, kaolin, montmorillonite, rectorite, illite, chlorite, pseudo-boehmite and silicon dioxide; or, The catalyst not containing molecular sieve is selected from catalysts prepared with one or more of the second raw materials treated by acid washing, calcination and sieving as raw materials, wherein the second raw materials include amorphous silica-alumina, clay, kaolin, montmorillonite, rectorite, illite and chlorite; or selected from catalysts prepared with one or more of the second raw materials treated by acid washing, calcination and sieving and pseudo-boehmite and / or silicon dioxide as raw materials; Optionally, the coal tar powder is coal powder and / or petroleum coke powder.

[0049] In one embodiment, the regeneration treatment is carried out in a dense fluidized bed regenerator; preferably, the process conditions of the regeneration treatment include: an air residence time of 0.5 to 60 seconds, preferably 1.0 to 10 seconds, a gasification temperature of the dense bed of 600 to 750°C, preferably 600 to 700°C, an oxygen-containing gas of 10 to 50% by volume, and a linear velocity of the dense bed of 0.05 to 0.6 m / s, preferably 0.2 to 0.4 m / s.

[0050] In one embodiment, the waste plastic preliminary melting, liquefaction and dechlorination unit includes 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.

[0051] In a preferred embodiment, the process conditions of the hot melt dechlorination treatment include: a feed rate of 5~5000kg / h, preferably 100~4000kg / h; an outlet temperature of 150~370°C, preferably 300~330°C, a reaction time of 1~30min, preferably 1~20min; the vacuum degree of the waste plastic preliminary melting and liquefaction dechlorination unit is 50~300mmHg, preferably 50~150mmHg.

[0052] In a specific embodiment, the particle size of the dechlorinated waste plastic particles obtained by pulverization is 100-2000 μm.

[0053] In the present disclosure, the apparatus and method for cooling treatment and pulverizing treatment may be conventional apparatus and method in the art.

[0054] In one embodiment, the waste plastics to be processed include one or more of LDPE, HDPE, PS, PP, PET and PVC; In one embodiment, the chlorine content in the waste plastic to be processed is less than 10% by weight; the ash content in the waste plastic to be processed is 1-40% by weight, preferably 3-30% by weight.

[0055] 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 reaction oil and gas.

[0056] The second aspect of the present disclosure provides a processing system for plastic reduction, pyrolysis and catalytic cracking of waste plastics, such as Figure 1 As shown, the treatment system includes: a waste plastic liquefaction unit, a waste plastic viscosity reduction unit, a material heating unit, a pyrolysis reaction unit, a catalytic cracking reaction unit and a separation unit; The waste plastic liquefaction unit comprises an inlet for waste plastic to be processed and an outlet for liquefied waste plastic, and the waste plastic liquefaction unit is configured to liquefy the waste plastic to be processed; The waste plastic viscosity reduction unit comprises a liquefied waste plastic inlet, a liquefied waste plastic oil outlet and a first dry gas outlet, and the waste plastic viscosity reduction unit is configured to perform viscosity reduction and cracking treatment on the liquefied waste plastic; The material heating unit comprises a heating inlet and a heating outlet, wherein the heating inlet is connected to the liquefied waste plastic oil outlet of the waste plastic viscosity reduction unit, and the material heating unit is configured to heat the liquefied waste plastic oil after viscosity reduction and cracking; The pyrolysis reaction unit has a pyrolysis reactant inlet and a pyrolysis product outlet, the pyrolysis reactant inlet is connected to the heating outlet of the material heating unit, and the pyrolysis reaction unit is configured to perform pyrolysis reaction treatment on high-temperature liquefied waste plastics; The catalytic cracking reaction unit comprises a cracking feed inlet, a contact agent inlet, a reaction oil and gas outlet and a regenerated contact agent outlet; the cracking feed inlet is connected to the pyrolysis product outlet of the pyrolysis reaction unit, and the contact cracking reaction unit is configured to perform a cracking reaction on the waste plastic pyrolysis reaction oil and gas; The separation unit includes a separation inlet, a second dry gas outlet, a liquefied gas outlet, a gasoline fraction outlet, a diesel fraction outlet and a wax oil fraction outlet; the separation inlet is connected to the reaction oil and gas outlet of the catalytic cracking unit, and the separation unit is configured to separate the reaction oil and gas.

[0057] In one embodiment, the separation unit may include a distillation device, a fractionation device and a rectification device.

[0058] In one embodiment, the system further comprises a regeneration unit, a waste plastic preliminary melting and liquefaction dechlorination unit, and a hydrogen chloride absorption unit; The regeneration unit comprises a regenerated contact agent inlet, an oxygen-containing gas inlet, a regenerated contact agent outlet and a regenerated flue gas outlet; the regeneration unit is configured to regenerate the regenerated contact agent in the presence of oxygen to obtain a regenerated contact agent and a regenerated flue gas; the regenerated contact agent outlet is connected to the contact agent inlet of the catalytic cracking reaction unit; The regeneration unit further comprises a dry gas inlet, which is connected to the first dry gas outlet of the waste plastic viscosity reduction unit and / or the second dry gas outlet of the separation unit; The waste plastic preliminary melting, liquefaction and dechlorination unit comprises a chlorine-containing waste plastic raw material inlet, a hydrogen chloride-containing gas phase material outlet and a dechlorinated waste plastic liquid phase material outlet, and the waste plastic preliminary melting, liquefaction and dechlorination unit is configured to perform melting and dechlorination treatment on the chlorine-containing waste plastic raw material; the dechlorinated waste plastic liquid phase material outlet is connected to the waste plastic to be treated inlet of the waste plastic liquefaction unit; The hydrogen chloride absorption unit comprises a hydrogen chloride-containing gas phase material inlet, a hydrogen chloride absorbent and a dechlorination dry gas outlet; the hydrogen chloride-containing gas phase material inlet is connected to the hydrogen chloride-containing gas phase material outlet of the waste plastic preliminary melting and liquefaction dechlorination unit; Preferably, the waste plastic liquefaction unit comprises a heating liquefaction conveying device; optionally, the heating liquefaction conveying device comprises a first screw-type heating conveying device; preferably, the first screw-type heating conveying device is selected from a twin-screw heating conveying device with heating or a single-screw heating conveying device; Preferably, the waste plastic preliminary melting, liquefaction and dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw heating and conveying device or a single-screw heating and conveying device; Preferably, the waste plastic 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 comprises a non-condensable gas outlet, and the non-condensable gas outlet is arranged at the top of the waste plastic preliminary melting, liquefaction and dechlorination unit.

[0059] The process flow of the system provided by the above specific embodiments in the present disclosure specifically includes: Figure 1 As shown: The waste plastics or dehydrated and dechlorinated waste plastic particles stored in the waste plastic storage tank 1 enter the waste plastic preliminary melting, liquefaction and dechlorination unit 2, and after dehydration, deaeration and dechlorination, a gaseous material containing hydrogen chloride and a dechlorinated waste plastic material are obtained. The gaseous material containing hydrogen chloride is pumped into the hydrogen chloride absorption unit 10 through a vacuum system to contact with a hydrogen chloride absorbent for hydrogen chloride absorption treatment, thereby obtaining a chlorine-containing absorbent and dechlorinated dry gas, and a small amount of non-condensable gas is discharged through a pipeline 23. The waste plastic liquefaction unit adopts a rapid heating liquefaction conveying device 3. The dechlorinated waste plastic liquid phase material from the waste plastic preliminary melting liquefaction dechlorination unit 2 can be discharged from the device for cooling and crushing to obtain dechlorinated waste plastic particles, or can directly enter the rapid heating liquefaction conveying device 3 (waste plastic liquefaction unit) to obtain a molten dechlorinated waste plastic liquid phase material; the molten dechlorinated waste plastic liquid phase material enters the plastic reduction and viscosity reduction reactor 4 (waste plastic viscosity reduction unit) for plastic reduction and viscosity reduction cracking treatment to obtain a liquefied waste plastic oil with plastic reduction and viscosity reduction cracking; the liquefied waste plastic oil with plastic reduction and viscosity reduction cracking is sent to the heating furnace 5 (heating unit). After being heated by the heating furnace 5, the high-temperature liquefied waste plastic enters the pyrolysis reaction unit 6 for pyrolysis reaction to obtain pyrolysis products and coke with ash, and the coke with ash is unloaded from the bottom 25 of the pyrolysis reaction unit 6; the pyrolysis products enter the receiving unit through the pipeline 11 and the wax oil fraction from the separation unit 9 through the pipeline 24 The catalytic cracking reaction unit 7 performs a catalytic cracking reaction, and the regenerated agent enters the catalytic cracking reaction unit 7 through pipeline 18 and part of the fresh agent through pipeline 13, thereby obtaining reaction oil gas and contact agent to be regenerated; the reaction oil gas enters the subsequent separation unit 9 through pipeline 12 for separation treatment, wherein: the second dry gas exits the device from pipeline 22, and the liquefied gas, gasoline fraction, diesel fraction and part of the wax oil fraction exit the device from pipeline 16; the contact agent to be regenerated with char and the optional ash with char enter the regeneration unit 8 through pipeline 14, the coke on the contact agent to be regenerated and the cracked dry gas from pipeline 21 (including the first dry gas from pipeline 22 and / or the second dry gas from pipeline 15) and the air from pipeline 19 undergo a complete combustion reaction, the generated regenerated flue gas exits the device through pipeline 17, and can be directly discharged into the atmosphere after reaching the standard, the obtained regenerated contact agent is led out of the regeneration unit 7 through pipeline 18, and the balance agent and ash are discharged from pipeline 20.

[0060] The present disclosure is further described in detail below through examples. The raw materials used in the examples can all be obtained through commercial channels.

[0061] The contact agent SL-1 used is a cracking catalyst with a trade name of CRC-1 (produced by Qilu Petrochemical Company, and the average particle size of SL-1 is 65 μm.

[0062] The contact agent SL-2 used is quartz sand. The quartz sand is crushed and sieved. The average particle size of SL-2 is 300 μm.

[0063] In the following examples and comparative examples, the kinematic viscosity test (200° C.) of the visbroken liquefied waste plastic oil was performed using a rotational viscosity test method.

[0064] The analytical method for chlorine content in liquefied waste plastics is: Q / SH 3360 270-2018.

[0065] The particle size of the contact agent is measured by a particle size detector.

[0066] 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.

[0067] The cracking product distribution was obtained by simulated distillation NB / SH / T 0558-2016 method.

[0068] The gas composition of the cracking reaction product is determined by the Q / SH 3360 255-2016 method; the hydrocarbon composition in the cracking reaction product is determined by chromatography analysis.

[0069] In the following examples, the particle size of the particles obtained by the pulverization process ranges from 100 to 2000 μm.

[0070] The catalytic cracking reactor in the following examples and comparative examples is a fluidized bed reactor.

[0071] Example 1 The process system of this embodiment includes: a waste plastic storage tank 1, a waste plastic preliminary melting, liquefaction and dechlorination unit 2, a waste plastic liquefaction unit 3, a waste plastic viscosity reduction unit 4, a material heating unit 5, a pyrolysis reaction unit 6, a catalytic cracking reaction unit 7, a separation unit 8 and a hydrogen chloride absorption unit 9.

[0072] Waste agricultural film (chlorine content of 0.0162 wt%) was fed into the waste plastic preliminary melting and liquefaction dechlorination unit 2, which used a twin-screw heating and conveying device, with a feed rate of about 100 kg / h, an outlet temperature of 220°C, a treatment time of 6 min, a vacuum degree of 150 mmHg, a screw diameter of 30 mm, and an outlet pressure of 0.2 MPa. After hot melt dechlorination, dechlorinated waste plastic WP-1 was obtained, and the properties of the obtained dechlorinated waste plastic WP-1 are shown in Table 1.

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

[0074] The dechlorinated waste plastic WP-1 was sent to a screw heating and conveying equipment for liquefaction treatment, and was further heated to 400°C with a residence time of 6 minutes. The rotational viscosity was measured by sampling at 30 minutes, 50 minutes and 70 minutes of insulation (using an adiabatic upflow visbreaking reactor) to obtain visbreaking liquefied waste plastic oil (respectively recorded as WP-1-30, WP-1-50, and WP-1-70). The viscosity of the visbreaking liquefied waste plastic oil is shown in Table 2.

[0075] The WP-1-50 sample was first heated in a heating furnace to obtain heated liquefied waste plastics, the outlet temperature of the heating furnace was 500°C, and the steam injection amount was 0.5% by weight; then the heated liquefied waste plastics were sent to a pyrolysis reaction device (pyrolysis tower), pyrolyzed at 480°C for 2h to obtain pyrolysis products; SL-1 was used as a contact agent, and the obtained pyrolysis products and steam were sent to a catalytic cracking reaction unit (contact cracking reactor), contacted with the fluidized contact agent for cracking reaction, and reaction oil gas and contact agent to be produced were obtained, wherein the mass ratio of the contact agent to the waste plastic raw material was 7:1, and the process conditions of the cracking reaction included: the reaction temperature was 550°C, the weight hourly space velocity was 4h -1 The mass ratio of steam to the waste plastic to be treated is 0.1:1; the product distribution of the cracking reaction products is shown in Table 3.

[0076] Example 2 Refer to the process system in Example 1. Waste agricultural film (chlorine content of 0.0162% by weight) is fed into the waste plastic preliminary melting and liquefaction dechlorination unit 2, which uses a twin-screw heating and conveying device, with a feed rate of about 100kg / h, an outlet temperature of 300°C, a processing time of 6min, a vacuum degree of 70mmHg, a screw diameter of 30mm, and an outlet pressure of 0.2MPa to obtain dechlorinated waste plastic WP-2. The absorption process of the hydrogen chloride-containing gas obtained by the dechlorination treatment is the same as that of Example 1.

[0077] The dechlorinated waste plastic WP-2 was sent to a screw heating and conveying equipment for liquefaction treatment, and was further heated to 420°C with a residence time of 12 minutes; then it was kept at 420°C for 30 minutes (using an adiabatic upflow visbreaking reactor), and a sample was taken to measure the rotational viscosity (denoted as WP-2-30) to obtain a visbreaking liquefied waste plastic oil. The viscosity results of the visbreaking liquefied waste plastic oil are shown in Table 2.

[0078] The WP-2-30 sample was first heated in a heating furnace to obtain heated liquefied waste plastics, the outlet temperature of the heating furnace was 480°C, and the gas injection volume was 0.5% by weight; then the heated liquefied waste plastics were sent to a pyrolysis reaction device, pyrolyzed at 480°C for 2 hours to obtain pyrolysis products; SL-2 was used as a contact agent, and the pyrolysis products and steam were sent to a catalytic cracking reaction unit (contact cracking reactor) to contact with the fluidized contact agent for cracking reaction to obtain reaction oil gas and contact agent to be produced, wherein the mass ratio of the contact agent to the waste plastic raw material was 5:1, and the process conditions of the cracking reaction included: the reaction temperature was 550°C, the weight hourly space velocity was 4h -1 The mass ratio of steam to the waste plastic to be treated is 0.2:1; the product distribution of the cracking reaction products is shown in Table 3.

[0079] Example 3 The process system and process flow of Example 1 were used, and the same waste plastic raw material WP-1 was used, except that the mass ratio of the contact agent to the waste plastic raw material was 3:1. The product distribution of the cracking reaction products is shown in Table 6.

[0080] Example 4 The process system and process flow of Example 1 were used, and the same waste plastic raw material WP-1 was used. The only difference was that the cracking reaction conditions were changed, including: the reaction temperature was 500°C, the weight hourly space velocity was 4h -1 The mass ratio of steam to the waste plastic to be treated is 0.6:1. The product distribution of the cracking reaction products is shown in Table 6.

[0081] Example 5 The process system and process flow of Example 1 were used, and the same waste plastic raw material WP-1 was used. The only difference was that the cracking reaction conditions were changed, including: the reaction temperature was 480°C, the weight hourly space velocity was 5h -1 The mass ratio of steam to the waste plastic to be treated is 1.2:1. The product distribution of the cracking reaction products is shown in Table 6.

[0082] Example 6 The process system and process flow of Example 1 are adopted, and the same waste plastic raw material is used. The only difference is the operating conditions of the waste plastic preliminary melting, liquefaction and dechlorination unit, specifically including: the processing time is 2 minutes.

[0083] The dechlorinated waste plastic WP-6 was sent to a screw heating and conveying device for liquefaction treatment, and was further heated to 390°C for a residence time of 2 minutes, and then kept at 390°C for 50 minutes. The rotational viscosity was measured by sampling (denoted as WP-6-50) to obtain the visbreaking liquefied waste plastic oil. The viscosity results of the visbreaking liquefied waste plastic oil are shown in Table 2.

[0084] The cracking reaction conditions were the same as those in Example 1. The product distribution of the cracking reaction products is shown in Table 6.

[0085] Comparative Example 1 Referring to the process flow of Example 1, the same waste plastic raw material is used. The difference from Example 1 is that the pyrolysis product no longer enters the catalytic cracking unit, but directly exits the device. The outlet temperature of the heating furnace is 520°C; the steam injection amount is 0.5% by weight; and then the heated liquefied waste plastic is sent to the pyrolysis reaction device, pyrolyzed at 500°C for 2h, and the product distribution of the pyrolysis reaction product is shown in Table 3.

[0086] Comparative Example 2 Referring to the process flow of Example 1, the same waste plastic raw material is used. The difference from Example 1 is that the visbroken liquefied waste plastic oil is not subjected to heating treatment and pyrolysis reaction, but directly enters the catalytic cracking unit. The product distribution of the cracking reaction products is shown in Table 3.

[0087] Table 1 Properties of waste agricultural film particles

[0088] Table 2 Viscosity of plastics with reduced plasticity and viscosity

[0089] Table 3 Distribution of products of pyrolysis and catalytic cracking reaction of dry ash-free waste plastics

[0090] Table 4 Mass composition of dry gas and liquefied gas in the products of pyrolysis and catalytic cracking of waste plastics

[0091] Table 5 Hydrocarbon composition of waste plastics pyrolysis and catalytic cracking reaction products

[0092] Table 6 Distribution of products of pyrolysis and catalytic cracking reaction of dry ash-free waste plastics

[0093] As can be seen from Example 1, waste agricultural film is sent to the waste plastic preliminary melting liquefaction dechlorination unit for hot melt dechlorination treatment to obtain dechlorinated waste plastic WP-1, and WP-1 is sent to a twin-screw heating and conveying equipment. After viscosity reduction at 400°C for 30min, 50min and 70min, the viscosities at 200°C are 1520cp, 267.6cp and 586.2cp, respectively. The sample with a viscosity of 267.6cp obtained by viscosity reduction for 50min is selected, and the sample has a stable flow state. After being heated to 480°C, it is sent to a pyrolysis tower for pyrolysis reaction. After pyrolysis, it is sent to a contact cracking reactor for high-temperature contact cracking reaction with a contact agent SL-1, and then fractionated in a fractionating tower to obtain dry gas, liquefied gas, gasoline, diesel, wax oil and coke with yields of 2.73%, 26.0%, 37.98%, 4.64%, 0.96% and 25.83%, respectively. Among them, the yield of liquefied gas is higher, and more low-carbon olefins can be obtained. Since the SL-1 contact agent is an acidic catalyst, the gasoline and coke yields in the cracking reaction products obtained in Example 1 are relatively high. Combined with the data in Table 5, it can be seen that in the fraction above 350°C, the aromatics yield in the liquid phase product obtained in Example 1 is 98.4%, achieving more aromatics under the catalytic cracking reaction of contact agents of different properties. In addition, since the waste plastic contains a certain amount of polyester, and after a long period of oxidation, the raw materials contain a certain amount of oxygen, so the pyrolysis products contain a certain amount of CO and CO2.

[0094] As can be seen from Example 2, waste agricultural film is sent to the waste plastic preliminary melting and liquefaction dechlorination unit for hot melt dechlorination treatment to obtain dechlorinated waste plastic WP-2, and WP-2 is sent to a twin-screw heating and conveying device. After viscosity reduction at 420°C for 30 minutes, the viscosity at 200°C is 282.8.cp, and the sample has a stable flow state. After being heated to 480°C, it is sent to a pyrolysis tower for pyrolysis reaction. After pyrolysis, it is sent to a contact cracking reactor for high-temperature contact cracking reaction with contact agent SL-2, and the yields of dry gas, liquefied gas, gasoline, diesel, wax oil and coke obtained by fractionation in a fractionation tower are 4.61%, 6.34%, 7.91%, 21.84%, 55.08% and 4.11% respectively. Since the SL-2 contact agent is an inert contact agent, the coke yield in the cracking reaction product obtained in Example 2 is low. Combined with the data in Table 5, it can be seen that in the fraction above 350°C, the yield of paraffins and olefins in the liquid phase product obtained in Example 2 is 87.2%, achieving more light olefins under the catalytic cracking reaction of contact agents of different properties. In addition, since the waste plastic contains a certain amount of polyester, and after long-term oxidation, the raw material contains a certain amount of oxygen, so the pyrolysis product contains a certain amount of CO and CO2.

[0095] Combined with the data in Table 6, by comparing Example 1 with Example 3, it can be seen that controlling the mass ratio of the contact agent to the waste plastic within the specified range of the present disclosure can further increase the yield of liquefied gas in the cracking reaction product, thereby increasing the amount of light olefins obtained; by comparing Example 1 with Example 4 and Example 5, it can be seen that controlling the cracking reaction conditions within the preferred range of the present disclosure and the specified range of the present disclosure can further increase the yield of liquefied gas in the cracking reaction product, so that more light olefins can be obtained; by comparing Example 1 with Example 6, it can be seen that controlling the conditions of the hot melt dechlorination treatment within the preferred range of the present disclosure can further increase the coke yield.

[0096] By comparing Comparative Example 1 with Example 1 or Example 2, it can be seen that since no contact cracking reaction was performed in Comparative Example 1, combined with the data in Table 5, it can be seen that in the 180-350°C fraction section and the fraction section above 350°C, the aromatics yield in the cracking reaction product was only 8.9% and 5.1%, respectively. The process effect of producing more aromatics cannot be achieved by only using the pyrolysis reaction. However, the present disclosure can obtain chemical raw materials of different properties by adjusting the properties of the contact agent.

[0097] By comparing Comparative Example 2 with Example 1 or Example 2, it can be seen that although Comparative Example 2 can obtain a product composition similar to that of the embodiments of the present disclosure, since the molecular weight of the liquefied waste plastic is very large, it is difficult to enter the fluidized bed reactor without heating treatment, and the initial pyrolysis reaction products of the waste plastic cannot directly enter the fluidized bed reactor in the gas phase, resulting in higher process energy consumption for obtaining the target chemical product.

[0098] 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.

[0099] 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.

[0100] 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 processing waste plastics by pyrolysis and catalytic 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 waste plastic viscosity reducing unit for visbreaking treatment to obtain visbreaking liquefied waste plastic oil; S3, allowing the visbroken liquefied waste plastic oil to enter a material heating unit for heating treatment to obtain heated liquefied waste plastic and a first dry gas; S4, allowing the heated liquefied waste plastic oil to enter a pyrolysis reaction unit for pyrolysis reaction to obtain pyrolysis products of oil gas and coke; S5, allowing the pyrolysis product oil and gas to enter a catalytic cracking reaction unit, contact with a fluidized contact agent to perform a cracking reaction, and obtain reaction oil and gas and a contact agent to be produced; S6. Allow the reaction oil and gas to enter a separation unit for separation treatment to obtain a second dry gas, liquefied gas, a gasoline fraction, a diesel fraction and a wax oil fraction.

2. The processing method according to claim 1, characterized in that: The method further comprises: returning at least part of the wax oil fraction obtained in step S6 to the catalytic cracking reaction unit to continue the cracking reaction; Preferably, the weight ratio of the returned wax oil fraction to the pyrolysis product oil and gas is (0.1~1):

1.

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

4. The processing method according to claim 3, characterized in that: The method further includes: The gaseous material containing hydrogen chloride enters a hydrogen chloride absorption unit, contacts with a hydrogen chloride absorbent, and performs hydrogen chloride absorption treatment to obtain a chlorine-containing absorbent and dechlorinated dry gas; Optionally, the gaseous material containing hydrogen chloride enters the hydrogen chloride absorption unit under the action of a vacuum system; Wherein, the hydrogen chloride absorbent is water or an alkali solution with a pH greater than 7; optionally, the alkali solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide solution, sodium bicarbonate solution, sodium carbonate solution and ammonia water.

5. The processing method according to claim 1, characterized in that: The method further comprises: in step S3, the catalytic cracking reaction unit performs a cracking reaction to obtain charcoal ash; Optionally, the method further comprises: allowing the ash with carbon and the contact agent to be regenerated to enter a regeneration unit for regeneration treatment, and in the presence of oxygen, allowing the contact agent to be regenerated and the carbon on the ash with carbon to undergo a complete combustion reaction to obtain regenerated flue gas and regenerated contact agent; Preferably, the method further comprises: Allow at least a portion of the first dry gas and / or at least a portion of the second dry gas to enter the regeneration unit for regeneration treatment, so that the regenerated contact agent and the ash with carbon undergo a complete combustion reaction in the presence of oxygen and dry gas to obtain regenerated flue gas and regenerated contact agent; Preferably, based on the total weight of the contact agent to be regenerated, the carbon content of the contact agent to be regenerated is 0.5-5.0 wt %.

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

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

8. The processing method according to claim 1, characterized in that: In step S3, the material heating unit includes a heating furnace; Preferably, the process conditions of the heating treatment include: the outlet temperature of the heating furnace is 450°C~550°C, preferably 460°C~520°C, the residence time is less than 60s, preferably 30~50s; optionally, the steam injection amount is 0.5~5% by weight, optimized to 1~3% by weight.

9. The processing method according to claim 1, characterized in that: In step S4, the process conditions of the pyrolysis reaction include: the top pressure of the pyrolysis tower is 0.05~0.6MPa, preferably 0.1~0.3Mpa; the pyrolysis reaction temperature is 450~520℃, preferably 480~520℃; the pyrolysis tower operation cycle is 1~72h, preferably 8~24h.

10. The processing method according to claim 1, characterized in that: In step S5, the process conditions of the cracking reaction include: reaction temperature of 490-750°C, weight hourly space velocity of 1-100h -1 , the mass ratio of the contact agent to the waste plastic to be treated is (5~30):1; Preferably, the process conditions of the cracking reaction include: reaction temperature of 500-650°C, weight hourly space velocity of 3-60h -1 , the mass ratio of the contact agent to the waste plastic to be treated is (6~20):1; Preferably, the visbroken liquefied waste plastic oil and steam are allowed to enter a contact cracking reaction unit; preferably, the mass ratio of steam to the waste plastic to be treated is (0-1):1, preferably (0.05-0.5):

1.

11. The processing method according to claim 1, characterized in that: In step S5, the contact agent is one or more selected from silicon-aluminum material catalyst, quartz sand and coal coke powder; preferably, the particle size of the contact agent is 20-3000 μm; Optionally, the silicon-aluminum material is selected from a catalyst containing molecular sieves and / or a catalyst not containing molecular sieves; preferably, the catalyst containing molecular sieves is a catalyst containing one or more molecular sieves selected from X molecular sieve, Y molecular sieve, mordenite, ZSM-5, pillared clay molecular sieve and SAPO and / or a spent FCC catalyst; Preferably, the catalyst not containing molecular sieve is selected from a catalyst prepared with one or more of the first raw materials as raw materials, wherein the first raw material includes amorphous silica-alumina, clay, kaolin, montmorillonite, rectorite, illite, chlorite, pseudo-boehmite and silicon dioxide; or, The catalyst not containing molecular sieve is selected from catalysts prepared with one or more of the second raw materials treated by acid washing, calcination and sieving as raw materials, wherein the second raw materials include amorphous silica-alumina, clay, kaolin, montmorillonite, rectorite, illite and chlorite; or selected from catalysts prepared with one or more of the second raw materials treated by acid washing, calcination and sieving and pseudo-boehmite and / or silicon dioxide as raw materials; Optionally, the coal tar powder is coal powder and / or petroleum coke powder.

12. The processing method according to claim 5, characterized in that: The regeneration treatment is carried out in a dense fluidized bed regenerator; preferably, the process conditions of the regeneration treatment include: an air residence time of 0.5 to 60 seconds, preferably 1.0 to 10 seconds, a gasification temperature of the dense bed of 600 to 750°C, preferably 600 to 700°C, an oxygen-containing gas of 10 to 50% by volume, and a linear velocity of the dense bed of 0.05 to 0.6 m / s, preferably 0.2 to 0.4 m / s.

13. The processing method according to claim 3, characterized in that: The waste plastic preliminary melting, liquefaction and dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw heating and conveying device or a single-screw heating and conveying device; Preferably, the process conditions of the hot melt dechlorination treatment include: a feed rate of 5 to 5000 kg / h, preferably 100 to 4000 kg / h; an outlet temperature of 150 to 370°C, preferably 300 to 330°C, a reaction time of 1 to 30 min, preferably 1 to 20 min; a vacuum degree of the waste plastic preliminary melting and liquefaction dechlorination unit of 50 to 300 mmHg, preferably 50 to 150 mmHg; Preferably, the particle size of the dechlorinated waste plastic particles obtained by pulverization is 100-2000 μm.

14. The processing method according to claim 1, characterized in that: The waste plastics to be processed include one or more of LDPE, HDPE, PS, PP, PET and PVC; Optionally, the chlorine content in the waste plastic to be processed is less than 10% by weight; the ash content in the waste plastic to be processed is 1-40% by weight, preferably 3-30% by weight.

15. A processing system for plastic reduction, pyrolysis and catalytic cracking of waste plastics, characterized in that: The treatment system includes: a waste plastic liquefaction unit, a waste plastic viscosity reduction unit, a material heating unit, a pyrolysis reaction unit, a catalytic cracking reaction unit and a separation unit; The waste plastic liquefaction unit comprises an inlet for waste plastic to be processed and an outlet for liquefied waste plastic, and the waste plastic liquefaction unit is configured to liquefy the waste plastic to be processed; The waste plastic viscosity reduction unit comprises a liquefied waste plastic inlet, a liquefied waste plastic oil outlet and a first dry gas outlet, and the plastic reduction and viscosity reduction unit is configured to perform viscosity reduction and cracking treatment on the liquefied waste plastic; The material heating unit comprises a heating inlet and a heating outlet, wherein the heating inlet is connected to the liquefied waste plastic oil outlet of the waste plastic viscosity reduction unit, and the material heating unit is configured to heat the liquefied waste plastic oil after viscosity reduction and cracking; The pyrolysis reaction unit has a pyrolysis reactant inlet and a pyrolysis product outlet, the pyrolysis reactant inlet is connected to the heating outlet of the material heating unit, and the pyrolysis reaction unit is configured to perform a pyrolysis reaction on the heated liquefied waste plastic; The catalytic cracking reaction unit comprises a cracking feed inlet, a contact agent inlet, a reaction oil and gas outlet and a regenerated contact agent outlet; the cracking feed inlet is connected to the pyrolysis product outlet of the pyrolysis reaction unit, and the contact cracking reaction unit is configured to perform a cracking reaction on the waste plastic pyrolysis reaction oil and gas; The separation unit includes a separation inlet, a second dry gas outlet, a liquefied gas outlet, a gasoline fraction outlet, a diesel fraction outlet and a wax oil fraction outlet; the separation inlet is connected to the reaction oil and gas outlet of the catalytic cracking unit, and the separation unit is configured to separate the reaction oil and gas.

16. The processing system according to claim 15, characterized in that: The system also includes a regeneration unit, a waste plastic preliminary melting and liquefaction dechlorination unit and a hydrogen chloride absorption unit; The regeneration unit comprises a regenerated contact agent inlet, an oxygen-containing gas inlet, a regenerated contact agent outlet and a regenerated flue gas outlet; the regeneration unit is configured to regenerate the regenerated contact agent in the presence of oxygen to obtain a regenerated contact agent and a regenerated flue gas; the regenerated contact agent outlet is connected to the contact agent inlet of the catalytic cracking reaction unit; The regeneration unit further comprises a dry gas inlet, which is connected to the first dry gas outlet of the waste plastic viscosity reduction unit and / or the second dry gas outlet of the separation unit; The waste plastic preliminary melting, liquefaction and dechlorination unit comprises a chlorine-containing waste plastic raw material inlet, a hydrogen chloride-containing gas phase material outlet and a dechlorinated waste plastic liquid phase material outlet, and the waste plastic preliminary melting, liquefaction and dechlorination unit is configured to perform melting and dechlorination treatment on the chlorine-containing waste plastic raw material; the dechlorinated waste plastic liquid phase material outlet is connected to the waste plastic to be treated inlet of the waste plastic liquefaction unit; The hydrogen chloride absorption unit comprises a hydrogen chloride-containing gas phase material inlet, a hydrogen chloride absorbent and a dechlorination dry gas outlet; the hydrogen chloride-containing gas phase material inlet is connected to the hydrogen chloride-containing gas phase material outlet of the waste plastic preliminary melting and liquefaction dechlorination unit; Preferably, the waste plastic liquefaction unit comprises a heating liquefaction conveying device; optionally, the heating liquefaction conveying device comprises a first screw-type heating conveying device; preferably, the first screw-type heating conveying device is selected from a twin-screw heating conveying device with heating or a single-screw heating conveying device; Preferably, the waste plastic preliminary melting, liquefaction and dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw heating and conveying device or a single-screw heating and conveying device; Preferably, the waste plastic 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.

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