Processing method and processing system for pyrolysis cracking of waste plastics

Abstract

The invention relates to a processing method for pyrolysis cracking of waste plastics, which comprises the following steps: feeding the waste plastics to be treated into a waste plastic liquefaction-plastic reduction visbreaking unit, and sequentially carrying out liquefaction treatment and plastic reduction visbreaking treatment to obtain liquefied waste plastic oil subjected to plastic reduction visbreaking; feeding the liquefied waste plastic oil subjected to plasticity reduction and viscosity reduction cracking and a first wax oil fraction from a delayed coking device into a material heating unit, and carrying out heating treatment to obtain heated liquefied waste plastic; the heated liquefied waste plastics are fed into a pyrolytic reaction unit to be subjected to a pyrolytic reaction, and a pyrolytic product and coke are obtained; and feeding the pyrolysis product into a separation unit for separation treatment to obtain dry gas, liquefied gas, a gasoline fraction, a diesel fraction and a second wax oil fraction. And the waste plastic pyrolysis device and the residual oil delayed coking device are jointly operated, so that recycling, large-scale and continuous utilization of the waste plastic can be effectively realized.

Description

Technical Field

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

[0002] With the advancement of science and technology and industrial development, plastics are widely used as packaging materials in people's daily lives. Used waste plastics cannot be decomposed by themselves in nature. Only a few types of waste plastics can be reprocessed and reused through specific recycling channels. A large amount of waste plastics enters landfills in the form of domestic garbage. Since waste plastics are not easy to decompose, they occupy a lot of space. In recent years, the amount of waste plastics has increased, and it has become an urgent task to recycle waste plastics quickly and greenly.

[0003] The simplest chemical method to deal with 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 catalyst conditions to crack polymers into low molecular weight substances to obtain gasoline, kerosene, diesel fractions and some pyrolysis gases. 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.

[0004] At present, waste plastic oil recovery technology mainly includes waste plastic thermal cracking, catalytic thermal cracking and thermal cracking catalytic modification technology. Thermal cracking has the advantages of simple process, relatively less equipment investment, no catalyst required, and short reaction process, making thermal cracking the lowest unit oil cost compared to the other two technologies. General waste plastics in domestic garbage undergo high-temperature thermal cracking reaction between 380~500℃, with a fast cracking speed and a relatively simple product composition, which can be used as oil products or chemical raw materials.

[0005] CN109401774A discloses a waste plastic continuous pyrolysis system and a pyrolysis method thereof, the system comprises a loading device, a feeding device, a pyrolysis reactor and a slag discharge 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 unevenly heated, and coking and fouling are easily generated. CN112608761A discloses a solid heat carrier internal heating type waste plastic treatment process, which solves the problem that the existing waste plastic treatment process is difficult to scale up and has low thermal efficiency by using iron ore pellets as a heat carrier to heat the waste plastic. However, there is no dechlorination means in this process, which makes the impurity content in the pyrolysis oil too high. CN10461030A discloses a coking method for producing fuel oil from waste plastics. The method is to preheat high aromatic components and waste plastics or plastic oil in a raw material buffer tank, enter a tubular heating furnace for heating, and then spray into a delayed coking tower for coking reaction. The waste plastics mentioned in the method are one or more of polyethylene, polypropylene and polystyrene, and do not contain polyvinyl chloride (PVC), so it is impossible to process waste plastic raw materials mixed with polyvinyl chloride (PVC). CN112538363A discloses a method for co-converting waste plastics in a delayed coker unit. The method converts waste plastics together with petroleum residue raw materials. 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 are high-viscosity polymer melts formed during the melting process, which have a density difference problem with hydrocarbon raw materials. Therefore, 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

[0006] The purpose of the present disclosure is to provide a processing method and system for pyrolysis and cracking of waste plastics. The waste plastic pyrolysis device and the residual oil delayed coking device are operated together to effectively realize the resource-based, large-scale and continuous utilization of waste plastics.

[0007] In order to achieve the above-mentioned object, the present disclosure provides a first aspect of a processing method for pyrolysis and cracking of waste plastics, the method comprising: S1, sending the waste plastics to be treated into the waste plastic liquefaction-plastic reduction and viscosity reduction unit, and sequentially performing liquefaction treatment and plastic reduction and viscosity reduction treatment to obtain liquefied waste plastic oil with plastic reduction and viscosity reduction; S2, sending the deplasticized and viscous-cracked liquefied waste plastic oil and the first wax oil fraction from the delayed coking device into a material heating unit for heating treatment to obtain high-temperature liquefied waste plastic; wherein the initial distillation point of the first wax oil fraction is 300-350° C., and the final distillation point is 500-550° C.; S3, sending the high-temperature liquefied waste plastic into a pyrolysis reaction unit to perform a pyrolysis reaction to obtain pyrolysis products and coke; S4. The pyrolysis product enters a separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and a second wax oil fraction; wherein the initial distillation point of the second wax oil fraction is 300-350° C., and the final distillation point is 500-550° C.

[0008] Optionally, the weight ratio of the first wax oil fraction to the waste plastic to be processed is (0.2-5.0):1, preferably (0.2-2.0):1.

[0009] Optionally, the method further comprises: in step S2, the plasticity-reducing and viscous-breaking liquefied waste plastic oil is mixed with the first wax oil fraction and then fed into the material heating unit for heating treatment to obtain the high-temperature liquefied waste plastic.

[0010] Optionally, the method further comprises: mixing the liquid product obtained in step S4 with the liquid product from the delayed coking device for further processing.

[0011] Optionally, before step S1, the method further includes: The chlorine-containing waste plastic raw material enters the waste plastic melting, dehydration and dechlorination unit for melting, dehydration and dechlorination treatment to obtain a gas phase material containing hydrogen chloride and a dehydrated and dechlorinated waste plastic material; The dehydrated and dechlorinated waste plastic material is subjected to cooling treatment and crushing treatment in a cooling and crushing unit in sequence to obtain dehydrated and dechlorinated waste plastic particles; the dehydrated and dechlorinated waste plastic particles are allowed to enter the waste plastic liquefaction unit; or The dehydrated and dechlorinated waste plastic material is directly fed into the waste plastic liquefaction-plasticization and viscosity reduction unit.

[0012] 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.

[0013] Optionally, in step S1, the waste plastic liquefaction-plasticization and viscosity reduction unit uses a heating and conveying device to perform the liquefaction treatment; 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: outlet temperature of 370-500°C, preferably 380-450°C; residence time of 5-30 min, preferably 5-15 min; The waste plastic liquefaction-plastic reduction and viscosity reduction unit adopts a plastic reduction and viscosity reduction reactor to carry out the plastic reduction and viscosity reduction cracking treatment. Preferably, the plastic reduction and viscosity reduction reactor is an adiabatic plastic reduction and viscosity reduction reactor; Preferably, the process conditions of the plastic reduction and visbreaking treatment include: a reaction temperature of 370-450° C., preferably 380-420° C.; and a residence time of 2-120 min, preferably 2-60 min.

[0014] Optionally, in step S2, the material heating unit includes a heating furnace; Preferably, the process conditions of the heat treatment include: the outlet temperature of the heating furnace is 450-550°C, preferably 460-520°C, the residence time is less than 60s, preferably 30-50s; optionally, the steam injection amount is 0.5-5% by weight, preferably 1-3% by weight.

[0015] Optionally, in step S3, 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 450~500℃, preferably 480~500℃; the operation cycle of the pyrolysis tower is 1~72h, preferably 8~24h.

[0016] Optionally, the waste plastic melting, dehydration and dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw or single-screw conveying device; The process conditions of the melting dehydration and 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 170 to 350° 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 melting dehydration and dechlorination unit of 50 to 300 mmHg, preferably 50 to 150 mmHg; Preferably, the particle size of the dehydrated and dechlorinated waste plastic particles obtained by pulverization is 100-2000 μm.

[0017] Optionally, the waste plastics to be processed include one or more of LDPE, HDPE, PS, PP, PET and PVC; Optionally, the PVC content in the waste plastic to be processed is less than 3% by weight; the ash content in the waste plastic to be processed is 1 to 40% by weight, preferably 3 to 30% by weight; Preferably, the content of PE plastics in the waste plastics to be processed is 30% by weight or more, preferably 50% or more, or, The content of PE plastics and PP plastics in the waste plastics to be processed is more than 60%, preferably more than 80%.

[0018] The second aspect of the present disclosure provides a processing system for pyrolysis and cracking of waste plastics, the processing system comprising: a waste plastic liquefaction-plasticity reduction and viscosity reduction unit, a delayed coking wax oil fraction inlet, a material heating unit, a pyrolysis reaction unit and a separation unit; The waste plastic liquefaction-plasticity reduction and viscosity reduction unit comprises an inlet for waste plastic to be processed, an outlet for liquefied waste plastic, an inlet for liquefied waste plastic and an outlet for liquefied waste plastic oil. The waste plastic liquefaction-plasticity reduction and viscosity reduction unit is configured to liquefy the waste plastic to be processed and to perform plasticity reduction and viscosity reduction 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 liquefaction-plasticity reduction and viscosity reduction unit and the delayed coking wax oil fraction inlet, and the material heating unit is configured to heat the liquefied waste plastic oil subjected to plasticity reduction and viscosity reduction and the first wax oil fraction from the delayed coking unit; 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 material heating unit, and the pyrolysis reaction unit is configured to perform pyrolysis reaction treatment 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, the liquefied gas outlet, the gasoline fraction outlet, the diesel fraction outlet and the wax oil fraction outlet are respectively connected to the coking liquid product pipeline of the delayed coking device, and the separation unit is configured to separate and process the pyrolysis products.

[0019] Optionally, the system also includes a waste plastic melting, dehydration and dechlorination unit and a hydrogen chloride absorption unit; The waste plastic melting, dehydration and 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, dehydration and dechlorination unit is configured to dehydrate and dechlorinate 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, dehydration and dechlorination unit; Preferably, the waste plastic liquefaction-plasticization and viscosity reduction unit comprises a heating and conveying device; optionally, the heating and conveying device comprises 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 waste plastic melting, dehydration 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 liquefaction-plasticization and viscosity reduction unit further comprises a circulating oil inlet; the circulating oil inlet is connected to the wax oil fraction outlet of the separation unit; Optionally, the waste plastic melting, dehydration and dechlorination unit further includes a non-condensable steam outlet.

[0020] Through the above technical scheme, the present invention provides a processing method and processing system for pyrolysis and cracking of waste plastics. The present invention combines the operation of a waste plastic pyrolysis device with a residual oil delayed coking device, introduces the wax oil fraction in the delayed coking device and the liquefied waste plastic oil into a material heating unit, and the wax oil fraction in the residual oil delayed coking is rich in coking precursors such as polycyclic aromatic hydrocarbons, which is conducive to the pyrolysis reaction of the waste plastics and can also improve the structure of the delayed coking liquid phase product. In addition, the recycling process can carry more heat into the pyrolysis tower due to the condensation heat release, and the carbon content of the coke in the waste plastics is increased, so that the waste Plastics can be better gasified; on the other hand, the waste plastics to be treated are quickly liquefied to obtain liquefied waste plastics, and the liquefied waste plastics are sent to a plastic reduction and viscosity reduction reactor for plastic reduction and viscosity reduction cracking treatment, so as to reduce the viscosity of the liquefied waste plastics without coking and excessive cracking, and form uniform and fluid fluidized waste plastics that can be transported by a pump; then they 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, thereby realizing the resource utilization of waste plastics and reducing coke generation.

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

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

[0023] Description of Reference Numerals 1-waste plastic storage tank, 2-waste plastic melting, dehydration and dechlorination unit, 3-waste plastic heating and conveying equipment, 4-waste plastic liquefaction, plastic reduction and viscosity reduction tank, 5-material heating unit, 6-pyrolysis reaction unit, 7-separation unit, 8-hydrogen chloride absorption unit, 9-pipeline, 10-pipeline, 11-pipeline, 12-pipeline, 13-liquefied gas outlet, 14-diesel fraction outlet and gasoline fraction outlet, 15-dry gas outlet, 16-wax oil fraction outlet, 17-delayed coking wax oil fraction inlet, 18-pipeline. DETAILED DESCRIPTION

[0024] 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.

[0025] The first aspect of the present disclosure provides a method for processing waste plastic by pyrolysis and cracking, such as Figure 1 As shown, the method includes: S1, sending the waste plastics to be treated into the waste plastic liquefaction-plastic reduction and viscosity reduction unit, and sequentially performing liquefaction treatment and plastic reduction and viscosity reduction treatment to obtain liquefied waste plastic oil with plastic reduction and viscosity reduction; S2, sending the deplasticized and viscous-cracked liquefied waste plastic oil and the first wax oil fraction from the delayed coking device into a material heating unit for heating treatment to obtain heated liquefied waste plastic; wherein the first wax oil fraction has an initial distillation point of 300-350° C., preferably 320-350° C., and a final distillation point of 500-550° C., preferably 500-530° C.; S3, sending the heated liquefied waste plastic into a pyrolysis reaction unit to perform a pyrolysis reaction to obtain pyrolysis products and coke; S4. The pyrolysis product is allowed to enter a separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and a second wax oil fraction; wherein the initial distillation point of the second wax oil fraction is 300-350° C., preferably 320-350° C., and the final distillation point is 500-550° C., preferably 500-530° C.

[0026] The present invention combines a waste plastic pyrolysis device with a residual oil delayed coking device for operation, introduces the wax oil fraction in the delayed coking device and the liquefied waste plastic oil into a material heating unit, the wax oil fraction in the residual oil delayed coking is rich in coking precursors such as polycyclic aromatic hydrocarbons, is conducive to the pyrolysis reaction of the waste plastic, and can also improve the structure of the delayed coking liquid phase product, and the recycling process can carry more heat into the pyrolysis tower due to condensation heat release, the carbon content of coke in the waste plastic is increased, and the waste plastic can be better gasified; on the other hand, the waste plastic to be treated is quickly liquefied to obtain liquefied waste plastic, and the liquefied waste plastic is sent to a plastic reduction and viscosity reduction reactor for plastic reduction and viscosity reduction cracking treatment, so as to reduce the viscosity of the liquefied waste plastic without coking and excessive cracking, and form a uniform and fluidized waste plastic that can be transported by a pump; then the waste plastic is treated by a heating furnace or the like to quickly reach the pyrolysis reaction temperature, and the heated liquefied waste plastic is transported to the pyrolysis tower for pyrolysis reaction, thereby realizing the resource utilization of the waste plastic and reducing the generation of coke.

[0027] In a specific embodiment, the weight ratio of the first wax oil fraction: the waste plastic to be treated is (0.2-5.0):1, preferably (0.2-2.0):1.

[0028] Introducing the wax oil fraction and the liquefied waste plastic oil in the delayed coking device into the material heating unit according to the ratio in the above embodiment can further improve the subsequent pyrolysis reaction efficiency, enhance the utilization rate of waste plastic resources, and further improve the structure of the delayed coking liquid phase product.

[0029] In a preferred embodiment, the method further comprises: in step S2, the plastic-reduced and viscous-cracked liquefied waste plastic oil is mixed with the first wax oil fraction and then fed into the material heating unit for heating treatment to obtain the heated liquefied waste plastic.

[0030] According to the above-mentioned embodiment, the wax oil fraction in the delayed coking device is mixed with the liquefied waste plastic oil and then sent to the material heating unit, so that the heat generated in the recycling process can be more utilized, and the carbon content of coke in the waste plastic entering the pyrolysis tower is increased, so that the waste plastic can be better gasified, thereby further improving the utilization efficiency of waste plastic resources.

[0031] In a preferred embodiment, the method further comprises: mixing the liquid product obtained in step S4 with the liquid product from the delayed coking device for further processing.

[0032] Processing according to the above-mentioned implementation method can further improve the utilization efficiency of waste plastic resources.

[0033] In a preferred embodiment, before step S1, the method further comprises: The chlorine-containing waste plastic raw material enters the waste plastic melting, dehydration and dechlorination unit for melting, dehydration and dechlorination treatment to obtain a gas phase material containing hydrogen chloride and a dehydrated and dechlorinated waste plastic material; The dehydrated and dechlorinated waste plastic material is subjected to cooling treatment and crushing treatment in a cooling and crushing unit in sequence to obtain dehydrated and dechlorinated waste plastic particles; the dehydrated and dechlorinated waste plastic particles are allowed to enter the waste plastic liquefaction unit; or The dehydrated and dechlorinated waste plastic material is directly fed into the waste plastic liquefaction-plasticization and viscosity reduction unit.

[0034] In the present disclosure, the melting dehydration and dechlorination treatment 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.

[0035] 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.

[0036] The present invention uses a waste plastic melting, dehydration and dechlorination unit to decompose the chlorine in the 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 the waste plastic, and reducing the anti-corrosion pressure of subsequent equipment.

[0037] In one embodiment, in step S1, the waste plastic liquefaction-plasticization and viscosity reduction unit uses a heating and conveying device to perform the liquefaction treatment; 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; 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 1-30 min, preferably 1-15 min.

[0038] In one embodiment, the waste plastic liquefaction-plastic reduction and viscosity reduction unit uses a plastic reduction and viscosity reduction reactor to perform the plastic reduction and viscosity reduction cracking treatment. Preferably, the plastic reduction and viscosity reduction reactor is an adiabatic plastic reduction and viscosity reduction reactor; In a preferred embodiment, the process conditions of the plastic reduction and visbreaking treatment include: a reaction temperature of 370-450°C, preferably 380-420°C; a residence time of 2-120 min, preferably 2-60 min. According to the preferred visbreaking process conditions in this embodiment, a better viscosity reduction effect can be obtained.

[0039] In one embodiment, in step S2, the material heating unit includes a heating furnace; Preferably, the process conditions of the heat treatment include: the outlet temperature of the heating furnace is 450-550°C, preferably 460-520°C, the residence time is less than 60s, preferably 30-50s; optionally, the steam injection amount is 0.5-5% by weight, preferably 1-3% by weight.

[0040] In one embodiment, in step S3, 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 450~500℃, preferably 480~500℃; the operation cycle of the pyrolysis tower is 1~72h, preferably 8~24h.

[0041] In the present disclosure, the pyrolysis reaction unit may include a plurality of pyrolysis towers arranged in parallel.

[0042] In one embodiment, the waste plastic melting, dehydration 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; In a preferred embodiment, the process conditions of the melt dehydration and 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 170 to 350° C., a reaction time of 1 to 30 min, preferably 1 to 20 min; a vacuum degree of the waste plastic melt dehydration and dechlorination unit of 50 to 300 mmHg, preferably 50 to 150 mmHg; In a preferred embodiment, the particle size of the dehydrated and dechlorinated waste plastic particles obtained by pulverization is 100-2000 μm.

[0043] In the present disclosure, the apparatus and method for cooling treatment and pulverizing treatment may be conventional apparatus and method in the art.

[0044] 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 PVC content in the waste plastic to be processed is less than 3% by weight; the ash content in the waste plastic to be processed is 1 to 40% by weight, preferably 3 to 30% by weight; In a preferred embodiment, the content of PE plastics in the waste plastics to be processed is 30% by weight or more, preferably 50% or more, or The content of PE plastics and PP plastics in the waste plastics to be processed is more than 60%, preferably more than 80%.

[0045] 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.

[0046] The second aspect of the present disclosure provides a processing system for pyrolysis and cracking of waste plastics, such as Figure 1 As shown, the treatment system includes: a waste plastic liquefaction-plasticization and viscosity reduction unit, a delayed coking wax oil fraction inlet, a material heating unit, a pyrolysis reaction unit and a separation unit; The waste plastic liquefaction-plasticity reduction and viscosity reduction unit comprises an inlet for waste plastic to be processed, an outlet for liquefied waste plastic, an inlet for liquefied waste plastic and an outlet for liquefied waste plastic oil. The waste plastic liquefaction-plasticity reduction and viscosity reduction unit is configured to liquefy the waste plastic to be processed and to perform plasticity reduction and viscosity reduction 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 liquefaction-plasticity reduction and viscosity reduction unit and the delayed coking wax oil fraction inlet, and the material heating unit is configured to heat the liquefied waste plastic oil subjected to plasticity reduction and viscosity reduction and the first wax oil fraction from the delayed coking unit; 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 material heating unit, and the pyrolysis reaction unit is configured to perform pyrolysis reaction treatment 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, the liquefied gas outlet, the gasoline fraction outlet, the diesel fraction outlet and the wax oil fraction outlet are respectively connected to the coking liquid product pipeline of the delayed coking device, and the separation unit is configured to separate and process the pyrolysis products.

[0047] In one embodiment, the separation unit may include a distillation device, a fractionation device and a rectification device.

[0048] In one embodiment, the system further comprises a waste plastic melting, dehydration and dechlorination unit and a hydrogen chloride absorption unit; The waste plastic melting, dehydration and 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, dehydration and dechlorination unit is configured to dehydrate and dechlorinate 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, dehydration and dechlorination unit; Preferably, the waste plastic liquefaction-plasticization and viscosity reduction unit comprises a heating and conveying device; optionally, the heating and conveying device comprises 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 waste plastic melting, dehydration 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 liquefaction-plasticization and viscosity reduction unit further comprises a circulating oil inlet; the circulating oil inlet is connected to the wax oil fraction outlet of the separation unit; Optionally, the waste plastic melting, dehydration 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.

[0049] The process flow of the system provided by the above specific embodiments in the present disclosure specifically includes: Figure 1 As shown: The waste plastics or dehydrated and dechlorinated waste plastic particles stored in the waste plastic storage tank 1 enter the waste plastic melting, dehydration and dechlorination device 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 18. The dehydrated and dechlorinated waste plastics can be cooled and crushed out of the device to obtain dehydrated and dechlorinated waste plastic particles, or directly enter the waste plastic heating and conveying equipment 3 to obtain molten dechlorinated waste plastic liquid phase materials; the molten dechlorinated waste plastic liquid phase materials enter the waste plastic deplasticization and viscosity reduction unit 4 to undergo plastic deplasticization and viscosity reduction cracking treatment to obtain plastic deplasticization and viscosity reduction cracking liquefied waste plastic oil; the wax oil fraction in the delayed coking device enters the heating furnace 5 together with the plastic deplasticization and viscosity reduction cracking liquefied waste plastic oil through the pipeline 17, and after being heated by the heating furnace 5, the heated After the plastic-reduced and viscosity-reduced liquefied waste plastics enter the pyrolysis reaction unit 6 through pipeline 11 for pyrolysis reaction, pyrolysis products and coke with ash are obtained. The pyrolysis products enter the separation unit 7 through pipeline 12 for separation treatment. The dry gas exits the device from pipeline 15, the liquefied gas exits the device from pipeline 13, the gasoline fraction and the diesel fraction exit the device from pipeline 14, and the wax oil fraction exits the device from pipeline 16. The liquid product in the separation unit 7 can also be sent to the delayed coking liquid product pipeline and mixed with the delayed coking liquid product for further processing.

[0050] 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.

[0051] Among them, the properties of the wax oil samples from the delayed coking unit are shown in Table 6.

[0052] The kinematic viscosity of the visbroken liquefied waste plastic oil was tested by the rotational viscosity test method (200°C).

[0053] The analytical method for chlorine content in liquefied waste plastics is: Q / SH 3360 270-2018.

[0054] 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.

[0055] The distribution of pyrolysis reaction products was obtained by simulated distillation NB / SH / T 0829-2010 method.

[0056] The gas composition of the pyrolysis reaction product was determined by the RIPP 78-90 method; the hydrocarbon composition in the pyrolysis reaction product was determined by chromatography analysis.

[0057] In the following examples, the particle size of the particles obtained by the pulverization process ranges from 100 to 2000 μm.

[0058] Example 1 The process system of this embodiment includes: a waste plastic storage tank 1, a waste plastic melting, dehydration and dechlorination unit 2, a waste plastic heating and conveying device 3, a waste plastic liquefaction, plastic reduction and viscosity reduction tank 4, a material heating unit 5, a pyrolysis reaction unit 6, a separation unit 7, a hydrogen chloride absorption unit 8 and a delayed coking wax oil fraction inlet 17.

[0059] The waste agricultural film is sent to the waste plastic melting dehydration and dechlorination unit for melting dehydration and dechlorination treatment. During the dechlorination process, the gas phase material containing hydrogen chloride is extracted by a vacuum system and sent to the hydrogen chloride absorption unit to contact with the hydrogen chloride absorbent (NaOH solution) for hydrogen chloride absorption treatment. The waste plastic melting dehydration and dechlorination unit uses a twin-screw pump and a vacuum device connected to a twin-screw heating and conveying device. The feed rate is about 100kg / h, the outlet temperature is 220℃, the reaction time is 12min, the vacuum degree of the twin-screw pump is 70mmHg, the screw diameter of the twin-screw pump is 50mm, and the outlet pressure of the twin-screw pump is 0.2MPa. The waste plastic material is cooled and crushed to obtain dehydrated and dechlorinated waste plastic WP-1. The properties of the obtained dehydrated and dechlorinated waste plastic WP-1 are shown in Table 1.

[0060] The dehydrated and dechlorinated waste plastic WP-1 was sent into a screw pump and further heated to 400°C. The samples were kept at 400°C for 20 min, 40 min and 60 min, and were recorded as WP-1-20, WP-1-40, WP-1-60 respectively. The rotational viscosity of the samples was measured. The test results are shown in Table 2.

[0061] The WP-1-60 sample was sent to a material heating unit (heating furnace) for heating treatment to obtain heated liquefied waste plastics, the heating temperature was 500°C, the residence time was 50s, and the steam injection amount in the heating furnace was 1% by weight; then the obtained heated liquefied waste plastics and the wax oil sample from the delayed coking device were sent to a pyrolysis reaction unit (pyrolysis tower) for pyrolysis reaction, wherein the weight ratio of the heated liquefied waste plastics to the wax oil sample was 1:0.51; the top pressure of the pyrolysis tower was 0.1Mpa, the reaction temperature was 480°C, the operation cycle was 10h (pyrolysis tower switching operation time), and pyrolysis products were obtained.

[0062] The pyrolysis products were separated by a separation unit to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction. Product distribution test was carried out, and the distribution of pyrolysis reaction products is shown in Table 3 and Table 4, and the hydrocarbon composition of the liquid phase product in the pyrolysis reaction product is shown in Table 5.

[0063] Comparative Example 1 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 WP-1-60 sample was not mixed with the wax oil sample from the delayed coking unit, and the WP-1-60 sample was directly sent to the pyrolysis unit and pyrolyzed at 480°C for 2 hours to obtain pyrolysis products. The distribution of pyrolysis reaction products is shown in Tables 3 and 4, and the hydrocarbon composition of the liquid phase product in the pyrolysis reaction product is shown in Table 5.

[0064] Example 2 The process system of Example 1 was adopted. Plastic packaging materials containing LDPE, HDPE, PS, PP and PVC (mass percentage of 4:4:8:3:1) were crushed and dried as waste plastic raw materials (chlorine content of 2.9%), and the waste plastic raw materials were sent to the waste plastic melting dehydration and dechlorination unit for melting dehydration and dechlorination treatment. The waste plastic melting dehydration and dechlorination unit was the same as that in Example 1, with a feed rate of about 100 kg / h, a vacuum degree of the twin-screw pump of 100 mmHg, an outlet temperature of 320°C, and a reaction time of 12 min to obtain dehydrated and dechlorinated waste plastic WP-2. The properties of the obtained dehydrated and dechlorinated waste plastic WP-2 are shown in Table 1. The outlet temperature was changed during the test process, and the morphology and chlorine content of the waste plastic after transportation under different outlet temperature conditions were tested to obtain a series of liquefied dechlorinated waste plastics WP-2-1 to WP-2-5. The properties of the obtained liquefied dechlorinated waste plastics WP-2-1 to WP-2-5 are shown in Table 7. The absorption process of the hydrogen chloride-containing gas obtained by dechlorination treatment is the same as that in Example 1.

[0065] Then the dehydrated and dechlorinated waste plastic WP-2-3 was sent into a screw pump and further heated to 390°C for 0.2h (liquefaction process). After being kept at 390°C for 30min, 50min and 70min, the rotational viscosity was measured (using an adiabatic upflow visbreaking reactor) to obtain visbroken liquefied waste plastic oil (respectively recorded as WP-2-3-30, WP-2-3-50, and WP-2-3-70). The properties of the visbroken liquefied waste plastic oil are shown in Table 2.

[0066] The WP-2-3-70 sample was sent to the material heating unit (heating furnace) for heating treatment to obtain heated liquefied waste plastics, the heating temperature was 510°C, the residence time was 40s, and the steam injection amount in the heating furnace was 2% by weight; then the obtained heated liquefied waste plastics and the wax oil sample from the delayed coking unit were sent to the pyrolysis reaction unit (pyrolysis tower) for pyrolysis reaction, wherein the weight ratio of the heated liquefied waste plastics to the wax oil sample was 1:0.84; the top pressure of the pyrolysis tower was 0.1MPa, the reaction temperature was 480°C, the operation cycle was 8h (pyrolysis tower switching operation time), and pyrolysis products were obtained. The distribution of pyrolysis reaction products is shown in Tables 3 and 4, and the hydrocarbon composition of the liquid phase products in the pyrolysis reaction products is shown in Table 5.

[0067] 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 weight ratio of waste agricultural film to wax oil sample was 1:3. The product distribution of the pyrolysis reaction products is shown in Table 8.

[0068] Example 4 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 weight ratio of waste agricultural film to wax oil sample was 1:0.1. The product distribution of the pyrolysis reaction products is shown in Table 8.

[0069] Example 5 The process system and process flow of Example 1 are used, the only difference being the operating conditions of the melt dehydration and dechlorination treatment, specifically including: the reaction time is 2 minutes, the vacuum degree of the twin-screw heating and conveying equipment is 150 mmHg, and the screw diameter of the twin-screw heating and conveying equipment is 30 mm.

[0070] The dehydrated and dechlorinated waste plastic WP-5 was sent into a screw pump and further heated to 390°C. The residence time was 2 minutes. It was kept at 390°C for 50 minutes. The rotational viscosity was measured by sampling (denoted as WP-5-50) to obtain the visbreaking liquefied waste plastic oil. The viscosity results of the visbreaking liquefied waste plastic oil are shown in Table 2.

[0071] The cracking reaction conditions were the same as those in Example 1. The product distribution of the cracking reaction products is shown in Table 8.

[0072] Comparative Example 2 The process system and process flow of Example 2 were used, and the same waste plastic raw materials were used. The only difference was that the WP-2-3-70 sample was not mixed with the wax oil sample from the delayed coking unit, and the WP-2-3-70 sample was directly sent to the pyrolysis unit and pyrolyzed at 480°C for 10 hours to obtain pyrolysis products. The distribution of pyrolysis reaction products is shown in Tables 3 and 4, and the hydrocarbon composition of the liquid phase product in the pyrolysis reaction product is shown in Table 5.

[0073] Comparative Example 3 The real waste plastic (chlorine content is about 2.5 weight %) is fed into the waste plastic melting dehydration and dechlorination unit for melting dehydration and dechlorination treatment. The waste plastic melting dehydration and dechlorination unit is the same as that in Example 1, with a feed rate of about 100 kg / h, an outlet temperature of 300°C, and a reaction time of 12 min to obtain dehydrated and dechlorinated waste plastic WP-3. The properties of the obtained dehydrated and dechlorinated waste plastic WP-3 are shown in Table 1.

[0074] WP-3 was sent into a screw pump and further heated to 420°C. After being kept at 420°C for 30 minutes, a sample was taken and recorded as WP-3-30. The rotational viscosity of the sample was measured. The test results are shown in Table 2.

[0075] The WP-3-30 sample was sent into the pyrolysis device and sent to the material heating unit (heating furnace) for heating treatment to obtain heated liquefied waste plastics. The heating temperature was 480°C, the residence time was 50s, and the steam injection amount in the heating furnace was 1% by weight; then the obtained heated liquefied waste plastics were sent to the pyrolysis reaction unit (pyrolysis tower) for pyrolysis reaction. The top pressure of the pyrolysis tower was 0.1MPa, the reaction temperature was 480°C, and the operation cycle was 10h (pyrolysis tower switching operation time) to obtain pyrolysis products. The distribution of pyrolysis reaction products is shown in Tables 3 and 4, and the hydrocarbon composition of the liquid phase products in the pyrolysis reaction products is shown in Table 5.

[0076] Comparative Example 4 The wax oil sample in the delayed coking unit was directly sent to the pyrolysis reaction unit for pyrolysis reaction. The top pressure of the pyrolysis tower was 0.1MPa, the reaction temperature was 480℃, and the operation cycle was 10h (pyrolysis tower switching operation time) to obtain pyrolysis products. The distribution of pyrolysis reaction products is shown in Tables 3 and 4, and the hydrocarbon composition of the liquid phase products in the pyrolysis reaction products is shown in Table 5.

[0077] Table 1 Properties of dehydrated and dechlorinated waste plastics

[0078] Table 2 Viscosity of visbroken liquefied waste plastic oil

[0079] Table 3 Distribution of pyrolysis products of dry ash-free waste plastics

[0080] Table 4 Mass composition of dry gas and liquefied gas in the pyrolysis products of waste plastics

[0081] Table 5 Hydrocarbon composition of liquid products in the pyrolysis reaction products of waste plastics

[0082] Table 6 Properties of wax oil samples in delayed coking unit

[0083] Table 7 Properties of liquefied dechlorinated waste plastics

[0084] Table 8 Distribution of pyrolysis products of dry ash-free waste plastics

[0085] As can be seen from Example 1, waste agricultural film is sent to the waste plastic melting dehydration and dechlorination unit for melting dehydration and dechlorination treatment to obtain dehydrated and dechlorinated waste plastic WP-1, and WP-1 is sent to a screw pump. After plastic reduction and viscosity reduction at 400°C for 20min, 40min and 60min respectively, the viscosities at 200°C are 11760.0cp, 1400.0cp and 351.6cp respectively. The sample with a viscosity of 351.6cp obtained by plastic reduction and viscosity reduction for 60min is selected, and is sent to a pyrolysis tower for pyrolysis reaction after being heated to 500°C. The dry gas, liquefied gas, gasoline, diesel, wax oil and coke are obtained by fractionation in a fractionating tower with yields of 2.50%, 2.12%, 34.71%, 37.18%, 10.05% and 13.36% respectively.

[0086] From the comparison between Example 1 and Comparative Example 1, it can be seen that when wax oil is added to the raw material mainly composed of PE, the liquid phase product obtained in Example 1 undergoes a significant change compared with Comparative Example 1, and the aromatic content increases significantly. In the 180-350°C fraction, saturated hydrocarbons account for 65.3% by weight and aromatic hydrocarbons account for 17.3% by weight in Example 1. In the fraction above 350°C, saturated hydrocarbons + olefins account for 69.2% by weight and aromatic hydrocarbons account for 30.8% by weight in Example 1. Since an appropriate amount of coking wax oil is added in Example 1, the proportion of coking precursors in the raw material increases, and more heat is carried into the reactor, so that the coke yield in Example 1 is increased by 8.96 percentage points compared with Comparative Example 1.

[0087] As can be seen from Example 2, the waste plastic raw material with high chlorine content is sent to the waste plastic melting dehydration dechlorination unit for melting dehydration dechlorination treatment. When the dechlorination outlet temperature meets 300-330°C, most of the chlorine in the waste plastic is removed; when the dehydrated and dechlorinated waste plastic WP-2 is plasticized and viscosity-reduced for 30min, 50min and 70min at 390°C, the viscosity at 200°C is 543cp, 330.8cp and 268.5cp respectively. The sample with a viscosity of 268.5cp obtained by plasticizing and viscosity-reducing for 70min is selected, and after being heated to 480°C, it is sent to the pyrolysis tower for pyrolysis reaction, and the dry gas, liquefied gas, gasoline, diesel, wax oil and coke yields are 1.48%, 2.86%, 32.13%, 30.79%, 30.91% and 1.75% respectively obtained by fractionation in the fractionation tower. Compared with Comparative Example 2, the coke yield of Example 2 is increased.

[0088] Combined with the data in Table 8, by comparing Example 1 with Example 3, it can be seen that by controlling the weight ratio of the provided waste agricultural film to the wax oil sample within the preferred range of the present disclosure, the coke yield in the pyrolysis reaction product can be further improved; by comparing Example 1 with Example 4, it can be seen that by controlling the weight ratio of the provided waste agricultural film to the wax oil sample within the specified range of the present disclosure, and adding a wax oil sample of appropriate quality, the proportion of the condensation reaction in the pyrolysis tower can be effectively controlled to be within an appropriate range, so that the heat carried into the pyrolysis tower is sufficient to better gasify the waste plastic, thereby further improving the coke yield in the pyrolysis reaction product; by comparing Example 1 with Example 5, it can be seen that by controlling the conditions of the melting dehydration and dechlorination treatment within the preferred range of the present disclosure, the coke yield in the pyrolysis reaction product can be improved.

[0089] By comparing Example 2 with Comparative Example 2, it can be seen that since the wax oil sample of the delayed coking device was not introduced in Comparative Example 2, the pyrolysis reaction was directly carried out, the proportion of condensation reaction in the pyrolysis tower was low, and the heat carried into the pyrolysis tower was lower than that in Example 2, which reduced the gasification effect of the waste plastics. Therefore, the coke yield in the pyrolysis reaction product was lower than that in Example 2.

[0090] It can be seen from Comparative Example 3 that the real waste plastic with a high chlorine content is put into the waste plastic melting, dehydration and dechlorination unit for melting, dehydration and dechlorination treatment to obtain the dehydrated and dechlorinated waste plastic WP-3, and the WP-3 is sent to the screw pump. After plastic reduction and viscosity reduction at 420°C for 30 minutes, the viscosity at 200°C is 282.8cp. After being heated to 480°C, it is sent to the pyrolysis tower for pyrolysis reaction, and fractionated in the distillation tower to obtain dry gas, liquefied gas, gasoline, diesel, wax oil and coke with yields of 2.11%, 3.42%, 41.96%, 15.42%, 3.03% and 32.97% respectively. It can be seen from the hydrocarbon composition of the liquid phase product in the pyrolysis reaction product in Table 5 that after pyrolysis, the liquid phase product of Comparative Example 3 is mainly composed of paraffins and olefins. In the 180-350°C fraction, saturated hydrocarbons + olefins account for 72.8% by weight, and aromatic hydrocarbons account for 22.8% by weight; in the fraction above 350°C, saturated hydrocarbons + olefins account for 47.2% by weight, and aromatic hydrocarbons account for 42.2% by weight. It can be seen that the proportion of aromatic hydrocarbons in Comparative Example 3 increases, the coke yield is high, and the proportion of condensation reaction in the pyrolysis tower is high, so there is no need to add coker wax oil to increase the proportion of condensation reaction.

[0091] It can be seen from Comparative Example 4 that, combined with the data in Table 5, the wax oil sample in the delayed coking unit is introduced into the process of the present disclosure alone. After pyrolysis, the liquid phase product of Comparative Example 4 has saturated hydrocarbons + olefins accounting for 71% by weight and aromatic hydrocarbons accounting for 29% by weight in the 180-350°C fraction; saturated hydrocarbons + olefins accounting for 25.1% by weight and aromatic hydrocarbons accounting for 48.5% by weight in the fraction above 350°C. Compared with Table 6, it can be seen that the combined operation of the delayed coking unit and the process of the present disclosure can further effectively improve the structure of the delayed coking liquid phase product.

[0092] 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.

[0093] 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.

[0094] 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 pyrolysis and cracking of waste plastics, characterized in that: The method includes: S1, sending the waste plastics to be processed into the waste plastic liquefaction-plastic reduction and viscosity reduction unit, and sequentially performing liquefaction treatment and plastic reduction and viscosity reduction treatment to obtain liquefied waste plastic oil with plastic reduction and viscosity reduction; S2, sending the deplasticized and viscous-cracked liquefied waste plastic oil and the first wax oil fraction from the delayed coking device into a material heating unit for heating treatment to obtain heated liquefied waste plastic; wherein the initial distillation point of the first wax oil fraction is 300-350° C., and the final distillation point is 500-550° C.; S3, sending the heated liquefied waste plastic into a pyrolysis reaction unit to perform a pyrolysis reaction to obtain pyrolysis products and coke; S4. The pyrolysis product enters a separation unit for separation treatment to obtain dry gas, liquefied gas, gasoline fraction, diesel fraction and a second wax oil fraction; wherein the initial distillation point of the second wax oil fraction is 300-350° C., and the final distillation point is 500-550° C.

2. The processing method according to claim 1, characterized in that: The weight ratio of the first wax oil fraction to the waste plastic to be treated is (0.2-5.0):1, preferably (0.2-2.0):

1.

3. The processing method according to claim 1, characterized in that: The method further comprises: in step S2, the plastic-reduced and viscous-cracked liquefied waste plastic oil is mixed with the first wax oil fraction and then sent to the material heating unit for heating treatment to obtain the heated liquefied waste plastic.

4. The processing method according to claim 1, characterized in that: The method further includes: mixing the liquid product obtained in step S4 with the liquid product from the delayed coking device for further processing.

5. 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, dehydration and dechlorination unit for melting, dehydration and dechlorination treatment to obtain a gas phase material containing hydrogen chloride and a dehydrated and dechlorinated waste plastic material; The dehydrated and dechlorinated waste plastic material is subjected to cooling treatment and crushing treatment in a cooling and crushing unit in sequence to obtain dehydrated and dechlorinated waste plastic particles; the dehydrated and dechlorinated waste plastic particles are fed into a waste plastic liquefaction unit; or The dehydrated and dechlorinated waste plastic material is directly fed into the waste plastic liquefaction-plasticization and viscosity reduction unit.

6. The processing method according to claim 5, 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.

7. The processing method according to claim 1, characterized in that: In step S1, the waste plastic liquefaction-plasticization and viscosity reduction unit uses a heating and conveying device to perform the liquefaction treatment; 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: outlet temperature of 370-500°C, preferably 380-450°C; residence time of 1-30 min, preferably 1-15 min; The waste plastic liquefaction-plastic reduction and viscosity reduction unit adopts a plastic reduction and viscosity reduction reactor to carry out the plastic reduction and viscosity reduction cracking treatment. Preferably, the plastic reduction and viscosity reduction reactor is an adiabatic plastic reduction and viscosity reduction reactor; Preferably, the process conditions of the plastic reduction and visbreaking treatment include: a reaction temperature of 370-450° C., preferably 380-420° C.; and a residence time of 2-120 min, preferably 2-60 min.

8. The processing method according to claim 1, characterized in that: In step S2, the material heating unit includes a heating furnace; Preferably, the process conditions of the heat treatment include: the outlet temperature of the heating furnace is 450-550°C, preferably 460-520°C, the residence time is less than 60s, preferably 30-50s; optionally, the steam injection amount is 0.5-5% by weight, preferably 1-3% by weight.

9. The processing method according to claim 1, characterized in that: In step S3, 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 450~500℃, preferably 480~500℃; the operation cycle of the pyrolysis tower is 1~72h, preferably 8~24h.

10. The processing method according to claim 5, characterized in that: The waste plastic melting, dehydration and dechlorination unit comprises a second screw heating and conveying device and a vacuum device connected to the second screw heating and conveying device; preferably, the second screw heating and conveying device is selected from a twin-screw heating and conveying device or a single-screw heating and conveying device; The process conditions of the melting dehydration and 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 170 to 350° C., a reaction time of 1 to 30 min, preferably 1 to 20 min; a vacuum degree of the waste plastic melting dehydration and dechlorination unit of 50 to 300 mmHg, preferably 50 to 150 mmHg; Preferably, the particle size of the dehydrated and dechlorinated waste plastic particles obtained by pulverization is 100-2000 μm.

11. The processing method according to claim 1, characterized in that: The waste plastics to be processed include one or more of LDPE, HDPE, PS, PP, PET and PVC; Optionally, the PVC content in the waste plastic to be processed is less than 3% by weight; the ash content in the waste plastic to be processed is 1 to 40% by weight, preferably 3 to 30% by weight; Preferably, the content of PE plastics in the waste plastics to be processed is 30% by weight or more, preferably 50% or more, or, The content of PE plastics and PP plastics in the waste plastics to be processed is more than 60%, preferably more than 80%.

12. A processing system for pyrolysis and cracking of waste plastics, characterized in that: The treatment system includes: a waste plastic liquefaction-plastic reduction and viscosity reduction unit, a delayed coking wax oil fraction inlet, a material heating unit, a pyrolysis reaction unit and a delayed coking separation unit; The waste plastic liquefaction-plasticity reduction and viscosity reduction unit comprises an inlet for waste plastic to be processed, an outlet for liquefied waste plastic, an inlet for liquefied waste plastic and an outlet for liquefied waste plastic oil. The waste plastic liquefaction-plasticity reduction and viscosity reduction unit is configured to liquefy the waste plastic to be processed and to perform plasticity reduction and viscosity reduction 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 liquefaction-plasticity reduction and viscosity reduction unit and the delayed coking wax oil fraction inlet, and the material heating unit is configured to heat the liquefied waste plastic oil subjected to plasticity reduction and viscosity reduction and the first wax oil fraction from the delayed coking unit; 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 material heating unit, and the pyrolysis reaction unit is configured to perform pyrolysis reaction treatment on the heated liquefied waste plastic; The delayed coking 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, the liquefied gas outlet, the gasoline fraction outlet, the diesel fraction outlet and the wax oil fraction outlet are respectively connected to the coking liquid product pipeline of the delayed coking device, and the separation unit is configured to separate and process the pyrolysis products.

13. The processing system according to claim 12, characterized in that: The system also includes a waste plastic melting, dehydration and dechlorination unit and a hydrogen chloride absorption unit; The waste plastic melting, dehydration and 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, dehydration and dechlorination unit is configured to dehydrate and dechlorinate 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, dehydration and dechlorination unit; Preferably, the waste plastic liquefaction-plasticization and viscosity reduction unit comprises a heating and conveying device; optionally, the heating and conveying device comprises 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 waste plastic melting, dehydration 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 liquefaction-plasticization and viscosity reduction unit further comprises a circulating oil inlet; the circulating oil inlet is connected to the wax oil fraction outlet of the separation unit; Optionally, the waste plastic melting, dehydration and dechlorination unit further includes a non-condensable steam outlet.

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