A system and method for preparing multiple products by catalytic pyrolysis of waste plastics

Abstract

The present invention provides a system and method for catalytically pyrolyzing waste plastics to produce multiple products. This system belongs to the field of waste plastic pyrolysis and includes a plastic-based carbon source coupled air distribution unit, a catalyst circulation deposition unit, a pyrolysis oil condensation unit, and a hydrogen circulation enrichment unit. The system comprises: the plastic-based carbon source coupled air distribution unit for pyrolyzing the waste plastics and collecting pyrolysis gas and hydrogen-rich circulating gas to obtain a mixed gas, which is then fed into the catalyst circulation deposition unit; the catalyst circulation deposition unit for depositing the mixed gas to obtain carbon nanotubes, hydrogen-rich gas, and condensable gas, which is then fed into the pyrolysis oil condensation unit; the pyrolysis oil condensation unit for condensing the condensable gas to obtain pyrolysis oil, which is then fed into the hydrogen circulation enrichment unit; and the hydrogen circulation enrichment unit for collecting hydrogen-rich gas and providing hydrogen-rich circulating gas and hydrogen-rich gas. This system can effectively solve the problem of a single product in the catalytic pyrolysis of waste plastics, achieve high-value utilization of waste plastics, and realize continuous, industrialized production.

Description

Technical Field

[0001] The present invention belongs to the field of waste plastic pyrolysis, and more specifically, relates to a system and method for preparing multiple products by catalytic pyrolysis of waste plastic. Background Art

[0002] To address the severity of global warming, humanity's demand for green and clean energy is increasing. Organic solid waste, whose production has been steadily increasing in recent years, is precisely a neglected resource. Taking plastics as an example, the world generates over 100 million tons of plastic waste annually, and over 60% of this goes unused, resulting in wasted resources and environmental pollution. Converting waste plastics into high-value-added products such as carbon materials, gaseous fuels, liquid fuels, and industrial chemicals is an inevitable development direction for the high-value utilization of waste plastics. Catalytic pyrolysis of waste plastics is an important method for achieving high-value utilization of biomass.

[0003] Currently, there are few reports on catalytic pyrolysis systems for waste plastics. CN113604244B discloses a system and method for in-situ catalytic pyrolysis of waste plastics. This method primarily addresses the technical challenges of low liquid yield, high levels of heavy components and organochlorine in the oil, and ash in the oil during catalytic pyrolysis. However, it overlooks the main challenge of industrializing catalytic pyrolysis of waste plastics: low economic efficiency. The catalytic pyrolysis of waste plastics produces a single, low-value-added product, poor heat and mass transfer affects product quality, and high catalyst costs and susceptibility to deactivation significantly hinder the further development of the waste plastics recycling industry.

[0004] In summary, in order to achieve continuous and high-value utilization of waste plastics, it is urgent to solve the problems of low added value, single product, poor quality, high catalyst cost and easy deactivation in the catalytic pyrolysis of waste plastics. Summary of the Invention

[0005] In view of the defects of the prior art, the purpose of the present invention is to provide a system and method for preparing multiple products by catalytic pyrolysis of waste plastics, aiming to solve the problems of the existing waste plastic pyrolysis system in terms of single product, low product added value and high cost.

[0006] To achieve the above objectives, according to one aspect of the present invention, a system for preparing multiple products by catalytic pyrolysis of waste plastics is provided. The system comprises a plastic-based carbon source coupled with an air distribution unit, a catalyst circulation deposition unit, a pyrolysis oil condensation unit, and a hydrogen circulation enrichment unit, wherein:

[0007] The plastic-based carbon source coupled air distribution unit includes a feeder, a pyrolyzer and an air distribution box. The feeder is connected to the inlet of the pyrolyzer and is used to feed waste plastic to the pyrolyzer to pyrolyze it and generate pyrolysis gas; the inlet of the air distribution box is respectively connected to the outlet of the pyrolyzer and the hydrogen circulation enrichment unit, and is used to collect the pyrolysis gas and the hydrogen-rich circulation gas; the outlet of the air distribution box is connected to the catalyst circulation deposition unit, and is used to feed the mixture of the pyrolysis gas and the hydrogen-rich circulation gas into the catalyst circulation deposition unit;

[0008] The catalyst circulation deposition unit includes a continuous catalytic reaction component and a particle separator. The inlet of the continuous catalytic reaction component is connected to the outlet of the air distribution box, and a catalyst is provided inside the continuous catalytic reaction component for depositing the mixed gas to obtain carbon nanotubes, hydrogen-rich gas and condensable gas; one end of the particle separator is connected to the outlet of the continuous catalytic reaction component, and the other end is connected to the inlet of the pyrolysis oil condensation unit, for separating the carbon nanotubes and sending the hydrogen-rich gas and condensable gas to the pyrolysis oil condensation unit;

[0009] The outlet of the pyrolysis oil condensation unit is connected to the hydrogen circulation enrichment unit, which is used to condense the condensable gas to obtain pyrolysis oil and send the hydrogen-rich gas to the hydrogen circulation enrichment unit;

[0010] The hydrogen circulation enrichment unit includes a pressure stabilizing tank and a gas storage tank. The inlet of the pressure stabilizing tank is connected to the pyrolysis oil condensation unit, and the outlet is connected to the air distribution box and the gas storage tank respectively, for collecting hydrogen-rich gas and providing hydrogen-rich circulating gas and hydrogen-rich gas respectively; the gas storage tank is used to store excess hydrogen-rich gas, thereby realizing catalytic pyrolysis of waste plastics to prepare carbon nanotubes, pyrolysis oil and hydrogen-rich gas.

[0011] As a further preferred embodiment, the continuous catalytic reaction assembly includes a reactor, an opening regulator arranged inside the reactor, a sinking pipe and a catalyst feeding reaction column inserted into the reactor, the bottom of the reactor is provided with a fluidized air inlet nozzle for connecting to the outlet of the air distribution box to feed the mixed gas; the opening regulator divides the reactor into a lower growth zone and an upper screening zone, which includes two symmetrical and inwardly inclined baffles, and the bottom end of the baffle is connected to the inlet of the sinking pipe; the sinking pipe is close to the inner wall of the reactor; the catalyst feeding reaction column is used to provide catalyst to the growth zone; during operation, the mixed gas in the growth zone is deposited on the catalyst to form catalyst-carbon nanotube mixed particles, and some of the mixed particles enter the screening zone under the drive of the mixed gas, and the mixed particles that reach the preset carbon deposition amount enter the particle separator together with the hydrogen-rich gas and condensable gas, and the mixed particles that do not reach the preset carbon deposition amount are deposited under the guidance of the opening regulator and sent back to the growth zone through the sinking pipe to realize cyclic catalysis.

[0012] As a further preference, the angle between the baffle and the vertical direction is 30° to 60°.

[0013] As a further preferred embodiment, the pyrolysis oil condensation unit includes a heavy oil separator, a light oil separator, a liquid oil separator and an oil storage tank which are connected in sequence. The heavy oil separator is provided with a surface heat exchanger inside for separating out the heavy oil; the light oil separator is provided with a multi-stage condenser inside for separating out the light oil and feeding it into the liquid oil separator. At the same time, an air outlet is provided on the upper part of the light oil separator for connecting to a hydrogen circulation enrichment unit to feed in hydrogen-rich gas; the liquid oil separator is used to separate and purify the light oil to obtain aromatic compounds and feed them into the oil storage tank for storage.

[0014] According to another aspect of the present invention, a method for preparing multiple products by catalytic pyrolysis of waste plastics using the above system is provided, the method comprising the following steps:

[0015] S1 feeds the waste plastic into the pyrolyzer through the feeder for pyrolysis and generates pyrolysis gas, which enters the air distribution box through the first air inlet pipe. At the same time, the hydrogen circulation enrichment unit sends the hydrogen-rich circulation gas into the air distribution box through the second air inlet pipe;

[0016] The S2 air distribution box sends the mixture of pyrolysis gas and hydrogen-rich circulating gas into the continuous catalytic reaction component, where carbon nanotubes, hydrogen-rich gas and condensable gas are deposited under the action of the catalyst. The carbon nanotubes are separated by a particle separator and the hydrogen-rich gas and condensable gas are sent to the pyrolysis oil condensation unit.

[0017] S3 utilizes the pyrolysis oil condensation unit to condense the condensable gas to obtain pyrolysis oil and sends the hydrogen-rich gas into the pressure surge tank;

[0018] The S4 pressure stabilizing tank delivers the hydrogen-rich gas as hydrogen-rich circulating gas to the air distribution box, and delivers excess hydrogen-rich gas to the gas storage tank for storage.

[0019] As a further preference, in step S1, the pyrolysis temperature of the pyrolyzer is 480°C to 530°C, and the advancement time of the waste plastic is 20 minutes to 30 minutes.

[0020] As further preferred, in step S2, the volume ratio of the hydrogen-rich circulating gas to the pyrolysis gas in the mixed gas is 1:5 to 1:20.

[0021] As further preferred, in step S2, the catalyst is a eutectic catalyst formed by a bimetallic and a metal oxide support.

[0022] As a further preference, the flow rate of the fluidizing air inlet nozzle in the continuous catalytic reaction assembly is 0.8 m / s to 1.5 m / s.

[0023] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0024] 1. The present invention, by providing a plastic-based carbon source coupled with an air distribution unit, a catalyst circulation deposition unit, a pyrolysis oil condensation unit, and a hydrogen circulation enrichment unit, can utilize waste plastics for catalytic pyrolysis to produce a variety of products, including carbon nanotubes, hydrogen-rich gas, and pyrolysis oil. This effectively solves the problem of a single product in the catalytic pyrolysis of waste plastics, achieves high-value utilization of waste plastics, and enables continuous, industrialized production. Simultaneously, the present invention utilizes the hydrogen circulation enrichment unit to achieve a hydrogen-rich gas circulation function, increasing the hydrogen concentration in the mixed gas during continuous circulation. This not only effectively improves the quality of the produced hydrogen-rich gas, but also, in conjunction with good heat and mass transfer, enhances the stability of the catalyst, thereby improving the quality of the carbon nanotubes.

[0025] 2. In particular, the present invention optimizes the structure of the continuous catalytic reaction assembly and utilizes an aperture regulator to divide the reactor into a growth zone and a screening zone, allowing only mixed particles with a high carbon deposition rate to enter the carbon nanotube storage bin, thereby effectively improving catalyst utilization.

[0026] 3. At the same time, by optimizing the inclination angle of the baffle, the present invention can fully deposit the highly stable eutectic catalyst, thereby maximizing the deposition amount of carbon nanotubes and screening them online;

[0027] 4. In addition, the present invention also proposes a method for preparing multiple products by catalytic pyrolysis of waste plastics, wherein a eutectic catalyst formed by a bimetallic component and a metal oxide support is used. Due to the strong interaction between the active bimetallic component and the metal oxide support, the catalyst is more active and has a cycle life that can be increased by 20 to 50 times compared to traditional catalysts.

[0028] 5. In addition, the present invention also optimizes the parameters in the process of preparing multiple products by catalytic pyrolysis of waste plastics. By optimizing the pyrolysis temperature and the waste plastic advancement time, the quality of the carbon source obtained by pyrolysis of plastics can be improved, thereby regulating the product yield and quality. By optimizing the outlet flow rate of the mixed gas, the catalyst in the growth zone of the catalyst circulation deposition unit can be fluidized, thereby enhancing heat and mass transfer. By optimizing the ratio of hydrogen-rich circulating gas to pyrolysis gas, the production and quality of carbon nanotubes can be regulated. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the system structure for preparing multiple products by catalytic pyrolysis of waste plastics provided by an embodiment of the present invention;

[0030] Figure 2 It is a structural schematic diagram of a continuous catalytic reaction assembly provided by an embodiment of the present invention.

[0031] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0032] 1-Continuous catalytic reaction assembly, 1.1-Fluidized air inlet nozzle, 1.2-Opening regulator, 1.3-Sinking pipe, 2-Particle separator, 3-Catalyst feed reaction column, 4-Heavy oil separator, 5-Light oil separator, 6-Compressor, 7-Pressure stabilizing tank, 8-Lower solenoid valve, 9-Air storage tank, 10-Air distribution box, 11-Pyrolyzer, 12-Feeder, 13-Upper solenoid valve, 14-Carbon nanotube storage bin, 15 -Particle separator outlet pipe, 16-Heavy oil separator inlet pipe, 17-Surface heat exchanger, 18-Heavy oil separator outlet pipe, 19-Light oil separator inlet pipe, 20-Multi-stage condenser, 21-Light oil separator oil distribution pipe, 22-Liquid oil separator, 23-Oil storage tank, 24-Light oil separator outlet pipe, 25-Second air inlet pipe, 26-First air inlet pipe, 27-Air box outlet pipe, 28-Rotating blade. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] like Figure 1 As shown, according to one aspect of the present invention, a system for preparing multiple products by catalytic pyrolysis of waste plastics is provided, the system comprising a plastic-based carbon source coupled with an air distribution unit, a catalyst circulation deposition unit, a pyrolysis oil condensation unit, and a hydrogen circulation enrichment unit, wherein:

[0035] The plastic-based carbon source coupled air distribution unit includes a feeder 12, a pyrolyzer 11 and an air distribution box 10. The feeder 12 is connected to the inlet of the pyrolyzer 11 and is used to convey waste plastics to the pyrolyzer 11 for pyrolysis and generation of pyrolysis gas. A rotating blade 28 is provided inside the feeder 12 for crushing the waste plastics. The pyrolyzer 11 preferably adopts a spiral feeding pyrolyzer; the first air inlet pipe 26 of the air distribution box 10 is connected to the outlet of the pyrolyzer 11 for collecting pyrolysis gas, and the second air inlet pipe 25 is connected to the outlet of the hydrogen circulation enrichment unit for collecting hydrogen-rich circulating gas. The air distribution box outlet pipe 27 of the air distribution box 10 is connected to the catalyst circulation deposition unit for feeding a mixture of pyrolysis gas and hydrogen-rich circulating gas into the catalyst circulation deposition unit;

[0036] The catalyst circulation deposition unit includes a continuous catalytic reaction component 1, a particle separator 2 and a carbon nanotube storage bin 14. The continuous catalytic reaction component 1 preferably adopts a circulating catalytic fluidized bed, the inlet of which is connected to the air distribution box outlet pipe 27, and a catalyst is arranged inside it for depositing the mixed gas to obtain carbon nanotubes, hydrogen-rich gas and condensable gas; the particle separator 2 preferably adopts a cyclone separator, one end of which is connected to the outlet of the continuous catalytic reaction component 1, and the other end of which is connected to the inlet of the pyrolysis oil condensation unit through the particle separator outlet pipe 15, for separating carbon nanotubes and sending hydrogen-rich gas and condensable gas to the pyrolysis oil condensation unit; the carbon nanotube storage bin 14 is connected to the bottom end of the particle separator 2 for storing the separated carbon nanotubes;

[0037] The outlet of the pyrolysis oil condensation unit is connected to the hydrogen circulation enrichment unit, which is used to condense the condensable gas to obtain pyrolysis oil and send the hydrogen-rich gas into the hydrogen circulation enrichment unit. It includes a heavy oil separator 4, a light oil separator 5, a liquid oil separator 22 and an oil storage tank 23 connected in sequence. The heavy oil separator 4 is connected to the particle separator outlet pipe 15 through the heavy oil separator inlet pipe 16. A surface heat exchanger 17 is provided inside it for separating heavy oil. In order to prevent condensation blockage, the particle separator outlet pipe 15 and the heavy oil separator inlet pipe 16 are maintained at 300℃~35 0°C; the light oil separator 5 is connected to the heavy oil separator outlet pipe 18 through the light oil separator inlet pipe 19, and a multi-stage condenser 20 is provided inside the light oil separator 5 for separating the light oil and sending it to the liquid oil separator 22 through the light oil separator oil separation pipe 21. At the same time, an air outlet is provided on the upper part of the light oil separator 5, and is connected to the hydrogen circulation enrichment unit through the light oil separator outlet pipe 24, for sending the hydrogen-rich gas to the hydrogen circulation enrichment unit; the outlet of the liquid oil separator 22 is connected to the oil storage bin 23 for separation and purification to obtain aromatic compounds and send them to the oil storage bin 23 for collection;

[0038] The hydrogen circulation enrichment unit includes a compressor 6, a pressure-surge tank 7, a gas storage tank 9, an upper solenoid valve 13 and a lower solenoid valve 8. The compressor 6 is arranged between the light oil separator outlet pipe 24 and the pressure-surge tank 7 to provide power for the entire system, so that the catalyst inside the continuous catalytic reaction component 1 is fluidized, the heat transfer between the catalyst and the mixer is enhanced, and the catalyst selectivity is improved through the hydrogen-rich atmosphere and good heat and mass transfer, thereby improving the quality of carbon nanotubes and hydrogen-rich gas. The outlet of the pressure-surge tank 7 is provided with an upper solenoid valve 13 and a lower solenoid valve 8, which are used to control the flow rate of the hydrogen-rich circulating gas and the hydrogen-rich gas respectively. The concentration of the hydrogen-rich circulating gas continues to increase during the circulation. After stabilization, the hydrogen concentration of the gas storage tank 9 can reach more than 80%, thereby providing a high-concentration (60% to 70%) hydrogen atmosphere for the continuous catalytic reaction component 1 and enhancing the deposition of carbon nanotubes on the catalyst surface. The gas storage tank 9 is used to store excess hydrogen-rich gas.

[0039] Furthermore, the continuous catalytic reaction assembly 1 includes a reactor, an aperture regulator 1.2 disposed within the reactor, a downpipe 1.3, and a catalyst feed reaction column 3 inserted into the reactor. A fluidized air inlet nozzle 1.1 is provided at the bottom of the reactor for connection to an air distribution box outlet pipe 27 for feeding a mixed gas. The aperture regulator 1.2 divides the reactor into a lower growth zone and an upper screening zone. The regulator includes two symmetrical, inwardly inclined baffles, the bottom ends of which are connected to the inlet of the downpipe 1.3. The downpipe 1.3 is in close contact with the inner wall of the reactor. The catalyst feed reaction column 3 is fixedly connected to the upper opening of the reactor for providing catalyst.

[0040] During operation, the catalyst density in the growth zone is 3.9 g / cm 3 ~5g / cm 3 The mixed gas is deposited on the catalyst to form mixed particles of catalyst-carbon nanotubes with a density of 2.2 g / cm 3 ~4.9g / cm 3 Utilizing the low density of carbon nanotubes, the mixed particles are distributed in a gradient according to density in the reactor. When the density of the mixed particles is lower than 2.5 g / cm 3 When the mixed particles with high carbon deposition amount are driven by the mixed gas, they pass through the opening regulator 1.2 and enter the screening area. The mixed particles that have reached the preset carbon deposition amount enter the particle separator 2 together with the hydrogen-rich gas and the condensable gas. Some mixed particles that have been mistakenly carried out but have not reached the preset carbon deposition amount are deposited under the guidance of the opening regulator 1.2 and pressed into the growth area through the sinking pipe 1.3 to realize cyclic catalysis.

[0041] Preferably, the present invention utilizes the opening regulator 1.2 to realize the control of the number of catalyst cycles, so that the angle between the baffle and the vertical direction is 30° to 60°, which can fully deposit the eutectic catalyst with high stability, thereby maximizing the deposition amount of carbon nanotubes and screening them out online.

[0042] According to another aspect of the present invention, a method for preparing multiple products by catalytic pyrolysis of waste plastics using the above system is provided, the method comprising the following steps:

[0043] The S1 waste plastic is crushed by the rotating blades 28 of the feeder 12 and fed into the pyrolyzer 11. It is pyrolyzed once by rotary heating to obtain pyrolysis gas. Due to the rotation, the plastic is basically completely pyrolyzed, and the obtained trace ash is twisted into the ash storage bin at the end of the pyrolyzer. The pyrolysis gas enters the air distribution box 10 through the first air inlet pipe 26. At the same time, the hydrogen circulation enrichment unit feeds the hydrogen-rich circulating gas into the air distribution box 10 through the second air inlet pipe 25.

[0044] The S2 air distribution box 10 sends the mixture of pyrolysis gas and hydrogen-rich circulating gas into the continuous catalytic reaction component 1, and the catalyst feeding reaction column 3 sends the preheated catalyst into the growth zone. The mixed gas is deposited under the action of the catalyst to obtain carbon nanotubes, hydrogen-rich gas and condensable gas. The mixed gas carries the catalyst-carbon nanotube mixed particles through the outlet adjusted by the opening regulator 1.2, and controls the mixed particles that have reached the critical point to enter the screening area. They are further screened in the screening area. The mixed particles that have reached the preset carbon deposition amount are cyclone-sedimented by the particle separator 2 and enter the carbon nanotube storage bin 14. The mixed particles that have not reached the preset carbon deposition amount are accumulated at the upper end of the opening regulator 1.2 and are pressed into the growth zone through the sinking conduit 1.3 for re-catalysis. At the same time, the hydrogen-rich gas and condensable gas are sent to the pyrolysis oil condensation unit through the particle separator outlet pipe 15. The critical point and the preset carbon deposition amount are both determined by the angle of the second opening regulator 9.2 and the flow rate of the second mixed gas.

[0045] S3 utilizes the pyrolysis oil condensation unit to condense the condensable gas to obtain pyrolysis oil and sends the hydrogen-rich gas to the surge tank 7, wherein the heavy oil in the condensable gas adheres to the surface heat exchanger 17 and can be used as a heavy fuel product. The remaining condensable gas is cooled by the multi-stage condenser 20 to obtain light oil, which is sent to the liquid oil separator 22 through the light oil separator inlet pipe 19 for separation and purification to obtain aromatic products, and then sent to the oil storage tank 23 for storage. The aromatic products are mainly benzene, toluene, and paratoluene;

[0046] S4 hydrogen-rich gas is passed into compressor 6 to obtain high-pressure hydrogen-rich gas. The pressure-surge tank 7 sends the high-pressure hydrogen-rich gas into the air distribution box 10 as hydrogen-rich circulating gas, and sends the excess high-pressure hydrogen-rich gas into the gas storage tank 9 for storage, thereby realizing catalytic pyrolysis of waste plastics to prepare carbon nanotubes, hydrogen-rich gas, aromatic hydrocarbons and other products.

[0047] Furthermore, in step S1, the waste plastics include mixed plastics with polyethylene, polypropylene, polystyrene and other polyolefins as main components; the pyrolysis temperature of the pyrolyzer 11 is 480°C to 530°C, and the advancement time of the waste plastics is 20min to 30min.

[0048] Furthermore, in step S2, increasing the proportion of hydrogen-rich circulating gas can enhance the quality of carbon nanotubes and hydrogen-rich gas, but a high-concentration hydrogen atmosphere will also reduce the yield of carbon nanotubes; on the other hand, lowering the proportion of hydrogen-rich circulating gas can increase the yield of carbon nanotubes, but it will also reduce the quality of the product accordingly. Therefore, by cooperating with the upper solenoid valve 13 and the air distribution box 10, the volume ratio of hydrogen-rich circulating gas to pyrolysis gas in the mixed gas is controlled to be 1:5 to 1:20, which can achieve the regulation of carbon nanotube yield and quality, thereby better controlling the balance between the quality of carbon nanotube products and the output rate.

[0049] Furthermore, in step S2, the catalyst is a eutectic catalyst, which forms a eutectic structure by a bimetallic and a metal oxide carrier. The active bimetallic component has a strong interaction with the metal oxide carrier, and the cycle life is increased by 20 to 50 times compared with the traditional single metal catalyst; the setting of the screening area of ​​the continuous catalytic reaction component 1 and the sinking pipe 1.3 also maximizes the use of the high cycle characteristics of the eutectic catalyst. Only the catalyst-carbon nanotube mixed particles that reach a higher number of cycles can enter the carbon nanotube storage bin 14, which greatly improves the catalyst utilization efficiency.

[0050] The eutectic catalyst is preferably prepared by direct impregnation. The main preparation process is to uniformly disperse appropriate amounts of Fe(NO3)3·9H2O, Ni(NO3)3·6H2O, and γ-Al2O3 in anhydrous ethanol so that the mass ratio of FeNi alloy (Fe:Ni=3) to γ-Al2O3 is 1:9. After removing the anhydrous ethanol, the temperature is slowly raised (5°C / min) from room temperature to 800°C in an air atmosphere and then calcined for 2 hours to obtain the FeNi(31)-Al2O3 catalyst.

[0051] A hydrogen-rich circulating gas at a pressure of 10 MPa to 15 MPa is mixed with the pyrolysis gas as a motive force, and a mixed gas with a flow rate of 0.8 m / s to 1.5 m / s is provided at the fluidizing air inlet nozzle 1.1, so that the catalyst in the growth zone is fluidized, heat and mass transfer are enhanced, and the hydrogen-rich atmosphere and good heat and mass transfer are used to jointly improve the catalyst selectivity and thus improve the quality of the carbon nanotubes.

[0052] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A system for preparing multiple products by catalytic pyrolysis of waste plastics, characterized in that: The system includes a plastic-based carbon source coupled air distribution unit, a catalyst circulation deposition unit, a pyrolysis oil condensation unit and a hydrogen circulation enrichment unit, wherein: The plastic-based carbon source coupled air distribution unit comprises a feeder (12), a pyrolyzer (11) and an air distribution box (10), wherein the feeder (12) is connected to the inlet of the pyrolyzer (11) and is used to transport waste plastics to the pyrolyzer (11) to pyrolyze the waste plastics and generate pyrolysis gas; the inlet of the air distribution box (10) is respectively connected to the outlet of the pyrolyzer (11) and the hydrogen circulation enrichment unit and is used to collect the pyrolysis gas and the hydrogen-rich circulation gas; the outlet of the air distribution box (10) is connected to the catalyst circulation deposition unit and is used to transport the mixed gas of the pyrolysis gas and the hydrogen-rich circulation gas into the catalyst circulation deposition unit; The catalyst circulation deposition unit comprises a continuous catalytic reaction component (1) and a particle separator (2), wherein the inlet of the continuous catalytic reaction component (1) is connected to the outlet of the air distribution box, and a catalyst is arranged inside the continuous catalytic reaction component for depositing the mixed gas to obtain carbon nanotubes, hydrogen-rich gas and condensable gas; the continuous catalytic reaction component (1) comprises a reactor, an opening regulator (1.2) arranged inside the reactor, a sinking pipe (1.3) and a catalyst feeding reaction column (3) inserted into the reactor, the bottom of the reactor is provided with a fluidized air inlet nozzle (1.1) for connecting to the outlet of the air distribution box to feed the mixed gas; the opening regulator (1.2) divides the reactor into a lower growth zone and an upper screening zone, and comprises two symmetrical and inwardly inclined baffles, and the bottom ends of the baffles are connected to the sinking pipe. The catalyst feed reaction column (3) is used to supply catalyst to the growth zone; during operation, the mixed gas in the growth zone is deposited on the catalyst to form mixed particles of catalyst-carbon nanotubes, and part of the mixed particles are driven by the mixed gas to enter the screening zone, and the mixed particles that reach the preset carbon deposition amount enter the particle separator (2) together with the hydrogen-rich gas and the condensable gas, and the mixed particles that do not reach the preset carbon deposition amount are deposited under the guidance of the opening regulator (1.2) and sent back to the growth zone through the sinking pipe (1.3) to realize cyclic catalysis; one end of the particle separator (2) is connected to the outlet of the continuous catalytic reaction component (1), and the other end is connected to the inlet of the pyrolysis oil condensation unit, and is used to separate the carbon nanotubes and send the hydrogen-rich gas and the condensable gas to the pyrolysis oil condensation unit; The outlet of the pyrolysis oil condensation unit is connected to the hydrogen circulation enrichment unit, which is used to condense the condensable gas to obtain pyrolysis oil and send the hydrogen-rich gas to the hydrogen circulation enrichment unit; The hydrogen circulation enrichment unit comprises a pressure stabilizing tank (7) and a gas storage tank (9); the inlet of the pressure stabilizing tank (7) is connected to the pyrolysis oil condensation unit, and the outlet thereof is respectively connected to the air distribution box (10) and the gas storage tank (9), for collecting hydrogen-rich gas and providing hydrogen-rich circulating gas and hydrogen-rich gas respectively; the gas storage tank (9) is used to store excess hydrogen-rich gas, thereby realizing catalytic pyrolysis of waste plastics to prepare carbon nanotubes, pyrolysis oil and hydrogen-rich gas.

2. The system for preparing multiple products by catalytic pyrolysis of waste plastics according to claim 1, characterized in that: The included angle between the baffle and the vertical direction is 30° to 60°.

3. The system for preparing multiple products by catalytic pyrolysis of waste plastics according to claim 1, characterized in that: The pyrolysis oil condensation unit comprises a heavy oil separator (4), a light oil separator (5), a liquid oil separator (22) and an oil storage bin (23) connected in sequence. The heavy oil separator (4) is provided with a surface heat exchanger (17) for separating heavy oil; the light oil separator (5) is provided with a multi-stage condenser (20) for separating light oil and feeding it into the liquid oil separator (22); and the upper part of the light oil separator (5) is provided with an air outlet for connecting to a hydrogen circulation enrichment unit to feed hydrogen-rich gas; the liquid oil separator (22) is used to separate and purify the light oil to obtain aromatic compounds and feed them into the oil storage bin (23) for storage.

4. A method for preparing multiple products by catalytic pyrolysis of waste plastics using the system according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: S1 feeds the waste plastics into the pyrolyzer (11) through the feeder (12) for pyrolysis and generates pyrolysis gas, which enters the air distribution box (10) through the first air inlet pipe (26), and at the same time, the hydrogen circulation enrichment unit feeds the hydrogen-rich circulation gas into the air distribution box (10) through the second air inlet pipe (25); The S2 air distribution box (10) sends the mixture of pyrolysis gas and hydrogen-rich circulating gas into the continuous catalytic reaction component (1), and deposits carbon nanotubes, hydrogen-rich gas and condensable gas under the action of the catalyst, wherein the mixed gas in the growth zone of the reactor is deposited on the catalyst to form catalyst-carbon nanotube mixed particles, and part of the mixed particles enter the screening zone driven by the mixed gas, and the mixed particles that reach the preset carbon deposition amount enter the particle separator (2) together with the hydrogen-rich gas and condensable gas, and the mixed particles that do not reach the preset carbon deposition amount are deposited under the guidance of the opening regulator (1.2) and sent back to the growth zone through the sinking pipe (1.3) to realize cyclic catalysis, and then the carbon nanotubes are separated by the particle separator (2) and the hydrogen-rich gas and condensable gas are sent to the pyrolysis oil condensation unit; S3 utilizes the pyrolysis oil condensation unit to condense the condensable gas to obtain pyrolysis oil and sends the hydrogen-rich gas into a pressure-surge tank (7); The S4 pressure stabilizing tank (7) delivers the hydrogen-rich gas as hydrogen-rich circulating gas to the air distribution box (10), and delivers excess hydrogen-rich gas to the gas storage tank (9) for storage.

5. The method for preparing multiple products by catalytic pyrolysis of waste plastics according to claim 4, characterized in that: In step S1, the pyrolysis temperature of the pyrolyzer (11) is 480°C to 530°C, and the advancement time of the waste plastic is 20 minutes to 30 minutes.

6. The method for preparing multiple products by catalytic pyrolysis of waste plastics according to claim 4, characterized in that: In step S2, the volume ratio of the hydrogen-rich circulating gas to the pyrolysis gas in the mixed gas is 1:5 to 1:

20.

7. The method for preparing multiple products by catalytic pyrolysis of waste plastics according to claim 4, characterized in that: In step S2, the catalyst is a eutectic catalyst formed by a bimetallic catalyst and a metal oxide support.

8. The method for preparing multiple products by catalytic pyrolysis of waste plastics according to any one of claims 4 to 7, characterized in that: In step S2, the flow rate of the fluidizing air inlet nozzle (1.1) in the continuous catalytic reaction component (1) is 0.8 m / s to 1.5 m / s.

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