System for preparing light oil through co-liquefaction of waste plastics and heavy oil

Abstract

The utility model provides a system for preparing light oil by co-liquefaction of waste plastic and heavy oil, which comprises a waste plastic and heavy oil co-liquefaction unit, a gas-liquid separation unit and a wax oil catalytic cracking unit, the waste plastic and heavy oil co-liquefaction unit is connected in series through two stages of tubular reactors; the waste plastics and the heavy oil are converted into liquid products under mild conditions; the gas-liquid separation unit is used for performing fractional separation on a liquid product through a multi-stage high-pressure separator and a multi-stage low-pressure separator to obtain first-stage light oil, wax oil and first-stage heavy oil; the wax oil catalytic cracking unit is used for converting wax oil generated by the co-liquefaction unit into dry gas, secondary light oil and secondary heavy oil. According to the utility model, the recycling of heavy oil components is realized through the closed-loop circulation design, the coking problem is solved by adopting the high-solid-content product discharge pipeline, and the final total yield of light oil reaches more than 85%, which is obviously superior to that of the traditional process.

Description

Technical Field

[0001] This utility model belongs to the field of waste plastic resource recycling technology, specifically relating to a system for producing light oil by co-liquefying waste plastics and heavy oil. Background Technology

[0002] Currently, methods for treating waste plastics include physical recycling, chemical recycling, and energy recovery. Physical recycling, also known as mechanical recycling, generally involves sorting, crushing, and molding waste plastics to remanufacture plastic products. However, this method requires a high degree of precision in raw material sorting, resulting in lower quality remanufactured plastic products and limited recycling cycles. Energy recovery recovers heat through incineration, but this process generates a large amount of harmful gases, causing secondary pollution. Chemical recycling uses pyrolysis or gasification technologies to convert the organic components in waste plastics into small-molecule hydrocarbons. Chemical recycling has the following advantages: 1) It can handle mixed, contaminated, or repeatedly physically recycled waste plastics, with a wide range of raw material options; 2) Chemically recycled plastics are comparable in quality to "primary plastics" produced from fossil fuels, making them suitable for applications in fields with higher requirements for quality, hygiene, and performance, such as medical and food processing; 3) It can convert waste plastics into chemical raw materials for further plastic production, achieving true recycling; 4) Compared to energy recovery, chemical recycling has less carbon emission reduction. Therefore, chemical recycling is one of the methods for recycling and treating waste plastics.

[0003] Based on literature review and field surveys, the chemical conversion of waste plastics is considered the only process capable of achieving sustainable development. Pyrolysis, in particular, has attracted attention from researchers and companies worldwide due to its environmental friendliness and high yield. The traditional waste plastic pyrolysis process is rotary kiln pyrolysis (e.g., CN208200839U), which has the advantages of low technical barriers and low cost; however, its disadvantages are also significant. The pyrolysis oil yield is relatively low, requiring periodic shutdowns for coke removal. For example, the oil yield of waste plastics excavated from landfills is generally between 20-40%, mainly because the low thermal conductivity of plastics leads to excessive residence time in the rotary kiln, resulting in severe secondary pyrolysis. BP developed a fluidized bed pyrolysis technology for waste plastics, which achieves a pyrolysis oil yield of approximately 68%, a pyrolysis gas yield of approximately 12%, and a semi-coke yield of approximately 20%. Compared to traditional rotary kiln technology, the pyrolysis oil yield is significantly improved. However, this technology involves direct feeding of waste plastics, which easily agglomerates upon entering the fluidized bed and forming hot molten waste plastics. This has prevented further widespread adoption of this technology after the completion of a demonstration plant. Li Zifeng et al. proposed a fluidized bed cracking processing method and system for waste plastics (CN117660038A). This method sequentially liquefies and de-viscosifies waste plastics to obtain liquefied waste plastic oil, which is then further processed through cracking to yield dry gas, liquefied petroleum gas (LPG), gasoline fraction, diesel fraction, and wax oil fraction. While this technology can convert waste plastics, it suffers from problems such as complex process flow, susceptibility to coking and clogging, and low yield of light oil. Utility Model Content

[0004] To address the problems of poor mass and heat transfer, coking and blockage, and low light oil yield in the separate processing of waste plastics in existing technologies, the purpose of this invention is to provide a system for the co-liquefaction of waste plastics and heavy oil to produce light oil. By connecting two-stage reactors in series, discharging high-solids-content products, and coupling catalytic cracking online, the system achieves the synergistic conversion of waste plastics and heavy oil, significantly improving the light oil yield.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A system for producing light oil by co-liquefying waste plastics and heavy oil, comprising:

[0007] The waste plastic and heavy oil co-liquefaction unit is used to co-liquefy waste plastic and heavy oil into liquid products.

[0008] A gas-liquid separation unit, the inlet of which is connected to the outlet of the co-liquefaction unit, is used to separate the liquid product into primary light oil, wax oil and primary heavy oil;

[0009] The wax oil catalytic cracking unit has its inlet connected to the wax oil outlet of the gas-liquid separation unit, and is used to convert the wax oil into dry gas, secondary light oil and secondary heavy oil.

[0010] Furthermore, the waste plastic and heavy oil co-liquefaction unit includes a primary tubular reactor, a secondary tubular reactor, and a raw material mixing tank. The raw material mixing tank is used to mix heavy oil, waste plastic, dispersed catalyst, primary heavy oil, and secondary heavy oil into a slurry. The outlet pipeline of the raw material mixing tank is connected to the top inlet of the primary tubular reactor, the outlet pipeline of the primary tubular reactor is connected to the inlet of the secondary tubular reactor, and the inlet of the secondary tubular reactor is also connected to an oil-soluble catalyst pipeline.

[0011] Furthermore, the bottom of the primary tubular reactor is equipped with a high solids content product discharge pipeline for intermittently discharging materials with a solids content of 20%–60% to prevent coking.

[0012] Furthermore, the gas-liquid separation unit includes:

[0013] The primary thermal high-pressure gas-liquid separator has its top inlet connected to the outlet pipeline of the secondary tubular reactor, and is used to separate the reaction products into gas and liquid.

[0014] The inlet of the secondary cold high-pressure gas-liquid separator is connected to the top outlet pipeline of the primary hot high-pressure gas-liquid separator, and is used to further separate the gas into light oil.

[0015] The inlet of the secondary cold low-pressure gas-liquid separator is connected to the bottom outlet pipeline of the primary hot high-pressure gas-liquid separator, and is used to separate the liquid into light oil, wax oil and primary heavy oil.

[0016] The light oil outlet at the bottom of the secondary cold high-pressure gas-liquid separator and the light oil outlet at the top of the secondary cold low-pressure gas-liquid separator are combined to form the primary light oil.

[0017] Furthermore, the waste plastic and heavy oil co-liquefaction unit also includes a circulating hydrogen compressor. The inlet pipeline of the circulating hydrogen compressor is connected to the top outlet of the secondary cold high-pressure gas-liquid separator, and the outlet pipeline of the circulating hydrogen compressor is connected to the top inlet of the primary tubular reactor.

[0018] Furthermore, the wax oil catalytic cracking unit includes:

[0019] A catalytic cracking reactor, wherein the inlet of the catalytic cracking reactor is connected to the wax oil outlet pipeline in the middle of the secondary cold low-pressure gas-liquid separator, for catalytic cracking reaction of wax oil;

[0020] A catalytic cracking gas-liquid separator, the inlet of which is connected to the outlet pipeline of the catalytic cracking reactor, is used to separate the reaction products into dry gas, secondary light oil, and secondary heavy oil.

[0021] Furthermore, the system for co-liquefying waste plastics and heavy oil to produce light oil also includes a high-pressure pump, wherein:

[0022] The primary heavy oil outlet pipeline at the bottom of the secondary cold low-pressure gas-liquid separator is connected to the inlet of the high-pressure pump.

[0023] The secondary heavy oil outlet pipeline at the bottom of the catalytic cracking gas-liquid separator is connected to the inlet of the high-pressure pump.

[0024] The outlet of the high-pressure pump is connected to the raw material mixing tank, and is used to circulate and transport primary heavy oil and secondary heavy oil to the raw material mixing tank.

[0025] Furthermore, the system for co-liquefying waste plastics and heavy oil to produce light oil also includes a mixed light oil, which is formed by mixing the primary light oil from the gas-liquid separation unit and the secondary light oil from the wax oil catalytic cracking unit, wherein:

[0026] Furthermore, the primary light oil outlet pipeline of the gas-liquid separation unit merges with the secondary light oil outlet pipeline of the wax oil catalytic cracking unit, and together they are connected to a mixing tank or mixer.

[0027] The mixed light oil is output from the outlet of the mixing tank or mixer.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) This utility model adopts the method of co-liquefaction of waste plastic and heavy oil to achieve the synergistic conversion of waste plastic and heavy oil under mild conditions (300-430℃, 3-8MPa), which solves the problems of poor mass and heat transfer effect, high temperature and easy blockage of conveying system that exist in the separate processing of waste plastic.

[0030] (2) This utility model adopts a series connection mode of a primary tubular reactor and a secondary tubular reactor, which can flexibly adjust the reaction conditions and catalyst type. At the same time, a high solid content product discharge pipeline is set at the bottom outlet of the primary tubular reactor, which can discharge high solid content materials during the reaction period at any time, effectively solving the problem of reactor coking and blockage, and ensuring the long-term stable operation of the device.

[0031] (3) This system maximizes the conversion of waste plastics into light oil in two steps by online coupling of waste plastic co-liquefaction and catalytic cracking, realizing the closed-loop recycling and high-value utilization of waste plastics. It has technical advantages such as short process flow and high light oil yield.

[0032] (4) The primary and secondary heavy oils are circulated back to the raw material mixing tank by a high-pressure pump, and then mixed with fresh raw materials to participate in the reaction again, so as to realize the efficient reuse of heavy components and thus improve the resource utilization rate. Attached Figure Description

[0033] To more clearly illustrate the solutions in this utility model, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of a system for producing light oil by co-liquefying waste plastics and heavy oil, which is provided by this utility model.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. First-stage tubular reactor; 2. Second-stage tubular reactor; 3. Catalytic cracking reactor; 4. First-stage hot high-pressure gas-liquid separator; 5. Second-stage cold high-pressure gas-liquid separator; 6. Second-stage cold low-pressure gas-liquid separator; 7. Catalytic cracking gas-liquid separator; 8. Feed mixing tank; 9. Circulating hydrogen compressor; 10. High-pressure pump; 11. Heavy oil; 12. Waste plastics; 13. Dispersed catalyst; 14. Fresh hydrogen; 15. High-solids product discharge pipeline; 16. Oil-soluble catalyst; 17. Dry gas; 18. Light oil. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0038] Example 1

[0039] Please refer to Figure 1 A system for producing light oil by co-liquefying waste plastics and heavy oil, comprising:

[0040] The waste plastic and heavy oil co-liquefaction unit is used to co-liquefy waste plastic and heavy oil into liquid products.

[0041] A gas-liquid separation unit, the inlet of which is connected to the outlet of the co-liquefaction unit, is used to separate the liquid product into primary light oil, wax oil and primary heavy oil;

[0042] The wax oil catalytic cracking unit has its inlet connected to the wax oil outlet of the gas-liquid separation unit, and is used to convert the wax oil into dry gas, secondary light oil and secondary heavy oil.

[0043] This invention achieves maximum light oil production through the synergistic coupling of waste plastics and heavy oil co-liquefaction and wax oil catalytic cracking processes. It features a short process flow, stable operation, and high light oil yield.

[0044] Example 2

[0045] The system for producing light oil by co-liquefying waste plastics and heavy oil provided in Example 1 is further optimized. Specifically, the waste plastics and heavy oil co-liquefaction unit includes a primary tubular reactor 1, a secondary tubular reactor 2, and a raw material mixing tank 8. The raw material mixing tank 8 is used to mix heavy oil 11, waste plastics 12, dispersed catalyst 13, primary heavy oil, and secondary heavy oil into a slurry. The outlet pipeline of the raw material mixing tank 8 is connected to the top inlet of the primary tubular reactor 1, and the outlet pipeline of the primary tubular reactor 1 is connected to the inlet of the secondary tubular reactor 2. The inlet of the secondary tubular reactor 2 is also connected to an oil-soluble catalyst 16 pipeline. In this system, the primary tubular reactor 1 and the secondary tubular reactor 2 are arranged in series, and the reaction conditions and catalyst types can be flexibly adjusted for each.

[0046] Furthermore, heavy oil 11 includes vacuum residue, atmospheric residue, catalytic cracking slurry, coal tar, etc., and waste plastics 12 include one or more of PP, PE, PVC, PS, and ABS, with a particle size range of less than 100 mesh.

[0047] Furthermore, the primary tubular reactor 1 and the secondary tubular reactor 2 preferably operate at a temperature of 300-430℃, an operating pressure of 3-8MPa, and a reaction space velocity of 0.1-1.0h. -1 The hydrogen-to-oil ratio is 300-1000 NL / kg.

[0048] This system employs a co-liquefaction method of waste plastics and heavy oil to achieve the synergistic conversion of waste plastics and heavy oil under mild conditions (300-430℃, 3-8MPa), solving the problems of poor mass and heat transfer, high temperature, and easy blockage of the conveying system that exist when processing waste plastics alone.

[0049] Example 3

[0050] This embodiment further discloses, based on the above embodiments, that the waste plastic and heavy oil co-liquefaction unit also includes a circulating hydrogen compressor 9. The inlet pipeline of the circulating hydrogen compressor 9 is connected to the top outlet of the secondary cold high-pressure gas-liquid separator 5, and the outlet pipeline of the circulating hydrogen compressor 9 is connected to the top inlet of the primary tubular reactor 1.

[0051] The raw materials, heavy oil 11, waste plastics 12, dispersed catalyst 13, primary heavy oil (from the bottom residue of the secondary cold low-pressure gas-liquid separator 6 in the gas-liquid separation unit) and secondary heavy oil (from the bottom residue of the catalytic cracking gas-liquid separator 7 in the wax oil catalytic cracking unit), are mixed in the raw material mixing tank 8 to form a uniform slurry. This slurry is then mixed with hydrogen gas from the outlet of the circulating hydrogen compressor 9 in a pipeline and enters the top inlet of the primary tubular reactor 1. Under hydrogen conditions, the heavy oil and waste plastics undergo hydrocracking. The reaction products are mixed with oil-soluble catalyst 16 and enter the secondary tubular reactor 2 to continue the reaction. The outlet of the primary tubular reactor 1 is equipped with a high-solids product discharge pipeline 15 (wherein, the high-solids product is a mixture containing catalyst, unreacted coal powder, and heavy oil, with a solid particle content of 20%~60%). The high-solids reaction products are discharged intermittently to prevent coking and blockage of the reactor, effectively solving the problem of reactor coking and blockage and ensuring the long-term stable operation of the unit.

[0052] Example 4

[0053] The system for producing light oil by co-liquefying waste plastics and heavy oil provided in Example 2 is further optimized. Specifically, the gas-liquid separation unit includes a primary hot high-pressure gas-liquid separator 4, a secondary cold high-pressure gas-liquid separator 5, and a secondary cold low-pressure gas-liquid separator 6. The top inlet of the primary hot high-pressure gas-liquid separator 4 is connected to the outlet pipeline of the secondary tubular reactor 2, and is used to separate the reaction products into gas and liquid. The secondary cold high-pressure gas-liquid separator 5 is used to further separate the gas into light oil. Specifically, the inlet of the secondary cold high-pressure gas-liquid separator 5 is connected to the outlet pipeline of the secondary tubular reactor 2. The top outlet pipeline of the primary hot high-pressure gas-liquid separator 4 is connected, and the top outlet of the secondary cold high-pressure gas-liquid separator 5 is connected to the inlet of the circulating hydrogen compressor 9. The bottom of the secondary cold high-pressure gas-liquid separator 5 separates light oil, and the secondary cold low-pressure gas-liquid separator 6 is used to separate the liquid into light oil, wax oil and primary heavy oil. Specifically, the inlet of the secondary cold low-pressure gas-liquid separator 6 is connected to the bottom outlet pipeline of the primary hot high-pressure gas-liquid separator 4, and the top, middle and bottom of the secondary cold low-pressure gas-liquid separator 6 respectively obtain light oil, wax oil and primary heavy oil.

[0054] The primary hot high-pressure gas-liquid separator 4 (3-8MPa) combined with the secondary cold high-pressure gas-liquid separator 5 and the secondary low-pressure gas-liquid separator 6 enables rapid fractional separation of reaction products (gas, light oil, wax oil, heavy oil), reducing additional distillation steps.

[0055] Example 5

[0056] This embodiment further optimizes the system for co-liquefying waste plastics and heavy oil to produce light oil, building upon the previous embodiments. Specifically, it discloses a wax oil catalytic cracking unit comprising a catalytic cracking reactor 3 and a catalytic cracking gas-liquid separator 7. The catalytic cracking reactor 3 is used to perform catalytic cracking on the wax oil. Specifically, the inlet of the catalytic cracking reactor 3 is connected to the wax oil outlet pipeline in the middle of the secondary cold low-pressure gas-liquid separator 6, and the outlet of the catalytic cracking reactor 3 is connected to the inlet pipeline of the catalytic cracking gas-liquid separator 7. The catalytic cracking gas-liquid separator 7 is used to separate the reaction products into dry gas 17, secondary light oil, and secondary heavy oil. This system deeply cracks the wax oil produced by the gas-liquid separation unit through the catalytic cracking reactor 3, converting it into secondary light oil, increasing the total light oil yield to over 85% (compared to 60-70% in traditional processes).

[0057] Furthermore, the operating parameters of catalytic cracking reactor 3 are as follows:

[0058] Operating temperature: 430-520℃

[0059] Operating pressure: 0.1-0.3 MPa

[0060] Catalyst-to-oil ratio: 3-8 (mass ratio of catalyst to feed oil).

[0061] Reaction time: 0.2-1 second.

[0062] The lower operating temperature (430°C) of the catalytic cracking reactor 3 ensures that the wax oil is fully cracked into light oil, avoiding the residue of unreacted heavy components. The upper operating temperature (520°C) of the catalytic cracking reactor 3 prevents excessive cracking from generating too much dry gas (such as methane and ethane) or coke, which would reduce the yield of light oil.

[0063] The operating pressure of the catalytic cracking reactor 3 is 0.1-0.3 MPa, which is conducive to the cracking reaction of hydrocarbon molecules and at the same time inhibits the condensation and coking reaction.

[0064] The catalyst-to-oil ratio in catalytic cracking reactor 3 can be dynamically adjusted according to the mixing ratio of waste plastics and heavy oil.

[0065] If the reaction time in the catalytic cracking reactor 3 is too short (<0.2 seconds), the wax oil may not crack completely; if the reaction time is too long (>1 second), the tendency for thermal cracking will increase and the selectivity of the target product will decrease. Therefore, the reaction time in the catalytic cracking reactor 3 is preferably 0.2-1 seconds.

[0066] This system further integrates the primary heavy oil from the bottom of the secondary cold low-pressure gas-liquid separator 6 with the secondary heavy oil from the bottom of the catalytic cracking gas-liquid separator 7, returning them together via high-pressure pump 10 to the feed mixing tank 8 to participate in a new round of co-liquefaction reaction. This closed-loop design achieves efficient utilization of all components of waste plastics and heavy oil, reduces waste emissions, and increases the total yield of light oil to over 85%.

[0067] It is worth mentioning that the light oil output from the bottom of the secondary cold high-pressure gas-liquid separator 5 and the light oil output from the top of the secondary cold low-pressure gas-liquid separator 6 are mixed to form primary light oil. The primary and secondary light oils are then mixed to form mixed light oil 18. Specifically, the primary light oil outlet pipeline of the gas-liquid separation unit and the secondary light oil outlet pipeline of the wax oil catalytic cracking unit converge and are connected to a mixing tank or mixer. The mixed light oil 18 is output from the outlet of the mixing tank or mixer. The mixing of primary and secondary light oils, by optimizing the distillation range distribution and physicochemical properties, significantly enhances the product value and application range of the light oil. The mixing process relies on a closed-loop system design to achieve efficient integration, which not only solves the limitations of single oil products but also strengthens the economic and environmental benefits of waste plastic resource utilization technology. This design embodies the dual innovation of "waste high-value utilization" and "process intensification."

[0068] Example 6

[0069] This embodiment further optimizes the system for producing light oil from waste plastics and heavy oil provided in the above embodiment. The system also includes a high-pressure pump 10, wherein: the primary heavy oil outlet pipeline at the bottom of the secondary cold low-pressure gas-liquid separator 6 is connected to the inlet of the high-pressure pump 10; the secondary heavy oil outlet pipeline at the bottom of the catalytic cracking gas-liquid separator 7 is connected to the inlet of the high-pressure pump 10; and the outlet of the high-pressure pump 10 is connected to the feedstock mixing tank 8. The high-pressure pump 10 is responsible for circulating the primary heavy oil (from the bottom of the secondary cold low-pressure gas-liquid separator 6) produced by the gas-liquid separation unit and the secondary heavy oil (from the bottom of the catalytic cracking gas-liquid separator 7) to the feedstock mixing tank 8, achieving closed-loop utilization of the heavy components and significantly improving the feedstock conversion rate and light oil yield.

[0070] The working principle of this utility model is as follows:

[0071] Heavy oil 11, waste plastics 12, and dispersible catalyst 13 are stirred in raw material mixing tank 8 to form a uniform slurry. After being mixed with circulating hydrogen and fresh hydrogen 14 from circulating hydrogen compressor 9 in a pipeline, the slurry enters the first-stage tubular reactor 1 and the second-stage tubular reactor 2 in sequence for hydrocracking reaction. The reaction products enter the first-stage high-pressure gas-liquid separator 4 to separate gaseous products and liquid products. The gaseous products are further separated by the second-stage cold high-pressure gas-liquid separator 5 to obtain light oil. The liquid products at the bottom of the first-stage hot high-pressure gas-liquid separator 4 enter the second-stage cold low-pressure gas-liquid separator 6, where they are separated to obtain light oil, wax oil, and first-stage heavy oil. The light oil is mixed with the light oil at the bottom of the second-stage cold high-pressure gas-liquid separator 5 to form first-stage light oil. Wax oil enters catalytic cracking reactor 3 and undergoes catalytic cracking reaction. The reaction products are separated by gas-liquid separator 7 to obtain dry gas, secondary light oil and secondary heavy oil. The secondary heavy oil is mixed with primary heavy oil and returned to the feed mixing tank by high pressure pump 10. The primary light oil and secondary light oil form mixed light oil 18.

[0072] This invention solves the problems of poor mass and heat transfer, coking and blockage, low light oil yield and complex process in traditional processes by using core technologies such as co-liquefaction and synergistic conversion of waste plastics and heavy oil, flexible control of two-stage reactors, discharge of high solids products and deep cracking of wax oil. It achieves efficient resource utilization of waste plastics and maximizes the production of light oil, combining technological advancement with economic and environmental benefits.

Claims

1. A system for co-liquefaction of waste plastics with heavy oil to produce light oil, characterized by: include The waste plastic and heavy oil co-liquefaction unit is used to co-liquefy waste plastic and heavy oil into liquid products. A gas-liquid separation unit, the inlet of which is connected to the outlet of the co-liquefaction unit, is used to separate the liquid product into primary light oil, wax oil and primary heavy oil; The wax oil catalytic cracking unit has its inlet connected to the wax oil outlet of the gas-liquid separation unit, and is used to convert the wax oil into dry gas, secondary light oil and secondary heavy oil.

2. The system for co-liquefaction of waste plastics with heavy oil to produce light oil according to claim 1, characterized in that: The waste plastic and heavy oil co-liquefaction unit includes a primary tubular reactor (1), a secondary tubular reactor (2), and a raw material mixing tank (8). The raw material mixing tank (8) is used to mix heavy oil (11), waste plastic (12), dispersed catalyst (13), primary heavy oil, and secondary heavy oil into a slurry. The outlet pipeline of the raw material mixing tank (8) is connected to the top inlet of the primary tubular reactor (1), the outlet pipeline of the primary tubular reactor (1) is connected to the inlet of the secondary tubular reactor (2), and the inlet of the secondary tubular reactor (2) is also connected to an oil-soluble catalyst (16) pipeline.

3. The system for co-liquefaction of waste plastics with heavy oil to produce light oil according to claim 2, characterized in that: The first-stage tubular reactor (1) is equipped with a high solids content product discharge pipeline (15) at the bottom, which is used to intermittently discharge materials with a solids content of 20%-60% to prevent coking.

4. The system for co-liquefaction of waste plastics with heavy oil to produce light oil according to claim 2, wherein, The gas-liquid separation unit includes: The first-stage hot high-pressure gas-liquid separator (4) has its top inlet connected to the outlet pipeline of the second-stage tubular reactor (2) to separate the reaction products into gas and liquid. The inlet of the secondary cold high-pressure gas-liquid separator (5) is connected to the top outlet pipeline of the primary hot high-pressure gas-liquid separator (4) for further separating the gas into light oil. The secondary cold low-pressure gas-liquid separator (6) has its inlet connected to the bottom outlet pipeline of the primary hot high-pressure gas-liquid separator (4) and is used to separate the liquid into light oil, wax oil and primary heavy oil. The light oil outlet at the bottom of the secondary cold high-pressure gas-liquid separator (5) and the light oil outlet at the top of the secondary cold low-pressure gas-liquid separator (6) are combined to form primary light oil.

5. The system for co-liquefaction of waste plastics with heavy oil to produce light oil according to claim 4, characterized in that: The waste plastic and heavy oil co-liquefaction unit also includes a circulating hydrogen compressor (9), the inlet pipeline of which is connected to the top outlet of the secondary cold high-pressure gas-liquid separator (5), and the outlet pipeline of the circulating hydrogen compressor (9) is connected to the top inlet of the primary tubular reactor (1).

6. The system for co-liquefaction of waste plastics with heavy oil to produce light oil according to claim 4, wherein, The wax oil catalytic cracking unit includes: The catalytic cracking reactor (3) is connected to the wax oil outlet pipeline in the middle of the secondary cold low-pressure gas-liquid separator (6) for catalytic cracking reaction of wax oil. The catalytic cracking gas-liquid separator (7) is connected at its inlet to the outlet pipeline of the catalytic cracking reactor (3) and is used to separate the reaction products into dry gas (17), secondary light oil and secondary heavy oil.

7. The system for co-liquefaction of waste plastics with heavy oil to produce light oil according to claim 6, wherein, The system also includes a high-pressure pump (10), wherein: The primary heavy oil outlet pipeline at the bottom of the secondary cold low-pressure gas-liquid separator (6) is connected to the inlet of the high-pressure pump (10); The secondary heavy oil outlet pipeline at the bottom of the catalytic cracking gas-liquid separator (7) is connected to the inlet of the high-pressure pump (10); The outlet of the high-pressure pump (10) is connected to the raw material mixing tank (8) for circulating and transporting primary heavy oil and secondary heavy oil to the raw material mixing tank (8).

8. The system for co-liquefaction of waste plastics with heavy oil to produce light oil according to any one of claims 1-7, wherein, It also includes a blended light oil (18), which is formed by mixing the primary light oil from the gas-liquid separation unit with the secondary light oil from the wax oil catalytic cracking unit, wherein: The primary light oil outlet pipeline of the gas-liquid separation unit merges with the secondary light oil outlet pipeline of the wax oil catalytic cracking unit and is connected to a mixing tank or mixer. The mixed light oil (18) is output from the outlet of the mixing tank or mixer.

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