Method for producing pyrolysis oil from waste plastics

Abstract

The present invention provides a method for producing waste plastic pyrolysis oil, comprising the steps of: (S1) supplying waste plastic raw material to a pyrolysis reactor to perform pyrolysis, and discharging the gas phase stream produced by the pyrolysis to the top and condensing it to obtain liquid oil; (S2) reducing the pressure of the oil remaining in the bottom of the pyrolysis reactor and condensing it to obtain further liquid oil; and (S3) refining the liquid oil obtained in steps (S1) and (S2), wherein the pyrolysis is performed by adjusting the internal pressure of the reactor to a range of more than 1 bar to 40 bar.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2023-0061366 dated 11 May 2023, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to a method for producing waste plastic pyrolysis oil, and more specifically, to a method for improving the pyrolysis efficiency of waste plastics and producing light hydrocarbon oil in high yield. [Background technology]

[0003] In recent years, the development and use of plastics with physical properties suited to various applications and purposes has increased. However, plastics require significant energy from crude oil extraction to manufacturing, and a large amount of carbon is emitted during this process. Furthermore, when plastics used in various products are discarded, environmental pollution and enormous disposal costs occur, making the recycling of waste plastics a crucial social issue.

[0004] Generally, there are three methods for recycling waste plastics (resins): mechanical recycling, chemical recycling, and thermal recycling. Mechanical recycling involves crushing and sorting the collected waste plastics, separating them by type, and then melting them into pellets using an extruder. The pellets are then mixed with new material in a certain proportion or reinforced with functional additives to produce resin products. Chemical recycling involves using various chemical means to extract only specific polymers or recover them as pure single molecules for repolymerization. Thermal recycling involves burning the waste plastics and recovering the resulting heat energy.

[0005] In particular, the aforementioned chemical recycling can reduce greenhouse gas emissions compared to the incineration of waste plastics, and has recently attracted attention in terms of alternative fuel development. For example, when waste plastics such as polyethylene or polypropylene are heated and thermally decomposed at a specific temperature, a gaseous stream of non-condensable gas and liquid oil is produced, and a highly viscous residual wax that has not been completely decomposed may be discharged. Of the thermal decomposition products, the liquid oil is becoming increasingly important as fuel oil for the manufacture of petrochemical products, and therefore, research is actively being conducted to increase the yield of the liquid oil.

[0006] The liquid oil produced by the thermal decomposition of the aforementioned waste plastic, i.e., the thermal decomposition oil, is usually a C2, such as naphtha. 5-12 This is a mixed oil containing light hydrocarbon oils and longer-chain hydrocarbon oils. When such a mixed oil contains a large amount of high-boiling-point components, the yield of high-value-added light hydrocarbon oil is limited, and there are problems with the production of heavy oil components and the discharge of residual wax.

[0007] To address these problems, methods have been proposed in which catalytic decomposition is carried out during the thermal decomposition of waste plastics, or in which heavy hydrocarbon (i.e., long-chain hydrocarbon) components in the thermal decomposition products of waste plastics are condensed using a contactor, and then recycled back into the thermal decomposition reactor for further thermal decomposition. However, these methods have limitations in improving the thermal decomposition efficiency of waste plastics and are limited to recycling as mixed oils. Therefore, there is a need for technology that can improve the waste plastic pyrolysis process and increase the yield of high-grade light hydrocarbon oil. [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem that the present invention aims to solve is, in order to solve the problems described in the background technology of the above invention, a method for improving the thermal decomposition efficiency of waste plastics and producing light hydrocarbon oil in high yield by adjusting the reaction pressure during the thermal decomposition of waste plastics to suppress the vaporization of high-boiling-point components and selectively increasing the residence time of liquid components. [Means for solving the problem]

[0009] To solve the above problems, according to one embodiment of the present invention, a method for producing waste plastic pyrolysis oil is provided, comprising the steps of (S1) supplying waste plastic raw material to a pyrolysis reactor and performing pyrolysis, discharging the gas phase stream generated by the pyrolysis to the top and then condensing it to obtain liquid oil, (S2) performing a reduced pressure treatment and condensation on the oil remaining at the bottom of the pyrolysis reactor to obtain further liquid oil, and (S3) purifying the liquid oil obtained in steps (S1) and (S2), wherein the pyrolysis is performed by adjusting the internal pressure of the reactor to a range of more than 1 bar to 40 bar. [Effects of the Invention]

[0010] According to the present invention, the decomposition efficiency of waste plastics can be improved by performing thermal decomposition of waste plastics under high-pressure conditions higher than atmospheric pressure to suppress the vaporization of high-boiling-point components and selectively increasing the residence time of liquid components in the reactor. This makes it possible to increase the selectivity and productivity of light hydrocarbon oils in the thermal decomposition products.

[0011] Furthermore, by applying a reduced pressure treatment to the oil remaining in the reactor after thermal decomposition under the aforementioned high-pressure conditions to increase the vaporization of liquid hydrocarbons, the yield of the pyrolysis oil can be further increased, and the discharge of residual wax can be minimized.

[0012] Furthermore, the utilization of the light hydrocarbon oil obtained by the thermal decomposition of waste plastics can reduce the emissions of greenhouse gases caused during the raw material supply in petrochemical processes, not only can improve process efficiency such as energy consumption reduction, but also is environmentally beneficial because no harmful gases are generated during the treatment of waste plastics.

Brief Description of Drawings

[0013] [Figure 1] This shows the results of high-pressure thermal decomposition of waste plastics (PE / PP mixture) in Example 1. [Figure 2] This shows the results of high-pressure thermal decomposition of waste plastics (PE / PP mixture) in Example 2. [Figure 3] This shows the results of high-pressure thermal decomposition of waste plastics (PE / PP mixture) in Example 3. [Figure 4] This shows the results of high-pressure thermal decomposition of waste plastics (PE / PP mixture) in Example 4. [Figure 5] This shows the results of high-pressure thermal decomposition of waste plastics (PE / PP mixture) in Example 5. [Figure 6] This shows the results of atmospheric pressure (1 bar) thermal decomposition of waste plastics (PE / PP mixture) in Comparative Example 1.

Modes for Carrying Out the Invention

[0014] The terms and words used in the description and claims of the present invention should not be construed as being limited to their ordinary or dictionary meanings. In accordance with the principle that the inventors can appropriately define the concepts of the terms in order to explain their invention in the best way, they should be construed in meanings and concepts consistent with the technical idea of the present invention.

[0015] As used in this application, the meaning of "include" or "contain" embodies a particular characteristic, domain, integer, step, operation, element, or component, and does not preclude the addition of other particular characteristics, domains, integers, steps, operations, elements, or components.

[0016] As used in this application, the term "stream" means the flow of fluid during a process, and may also mean the fluid itself flowing through piping. Specifically, the stream may simultaneously mean the fluid itself and the flow of fluid within the piping connecting each device. Furthermore, the fluid may contain one or more components of gas, liquid, and solid.

[0017] The term "C" used in this application n " represents all hydrocarbons having n carbon atoms, for example, "C 5-12 " represents all hydrocarbon molecules with 5 to 12 carbon atoms.

[0018] The term "liquid oil" as used in this application refers to a substance obtained when the gaseous stream obtained in the thermal decomposition step is converted into a liquid by condensation, and can also be called "liquid distilled oil." Furthermore, in this application, "pressure" means absolute pressure measured relative to a perfect vacuum.

[0019] A method for producing waste plastic pyrolysis oil according to one embodiment of the present invention includes (S1) a step of pyrolysis and condensation of waste plastic raw material, (S2) a step of heat treatment and condensation of residual oil, and (S3) a purification step.

[0020] The method for producing waste plastic pyrolysis oil according to the present invention will be described in detail step by step below. First, the waste plastic raw material is prepared and supplied to the pyrolysis reactor for thermal decomposition (S1).

[0021] The aforementioned waste plastic may contain natural polymers, synthetic polymers, or mixtures thereof, and the synthetic polymer may include thermoplastic resins such as polyethylene, polypropylene, and polystyrene. Furthermore, the thermoplastic resin may be a mixture with other types of resins such as PVC and PET, or thermosetting resins.

[0022] After being collected and sorted, such waste plastics may undergo a pretreatment process that includes crushing, washing, drying, and melting. The pretreatment process may be carried out in a manner that is common in the field.

[0023] For example, the size of the crushed waste plastic is not particularly limited, but is usually in the range of 0.5 to 6.0 cm. The crushed waste plastic, after being washed and dried, may then be fed into a tubular melting machine such as an extruder and melted. The extruder has the function of melting, kneading, and extruding, and may be, for example, a twin-screw extruder. If the waste plastic is a thermoplastic resin, such as polyethylene, polypropylene, or a mixture thereof, the melting temperature may be, but is not limited to, 120 to 350°C or 150 to 250°C.

[0024] The molten waste plastic obtained in the aforementioned pretreatment process is supplied to the pyrolysis reactor as a raw material. The pyrolysis reactor usable in this invention may be a stirred tank reactor equipped with an agitator (see Figures 1-5), and the agitator is not particularly limited as long as it can sufficiently agitate the molten waste plastic supplied as a raw material. For example, it may be a helical ribbon type or an anchor type, and maintaining a distance of about 5 mm to 1 cm from the inner wall of the reactor is advantageous for maximizing the agitation of the waste plastic and heat transfer through the reactor wall. Furthermore, the reactor can be operated in either a batch type or a continuous type. In addition, nitrogen purging may be performed on the reactor to maintain an oxygen-free or low-oxygen atmosphere while the pyrolysis reaction of the molten waste plastic is carried out.

[0025] The molten waste plastic is supplied to such a stirred reactor, and the reactor is heated while the agitator is operated to perform thermal decomposition of the molten waste plastic. The heating of the waste plastic may be carried out by passing high-temperature / high-pressure steam, hot water, or a heat transfer fluid through a jacket provided outside the reactor to transfer high-temperature heat to the waste plastic, and is not particularly limited to this method.

[0026] Conventional waste plastic pyrolysis processes are usually carried out under atmospheric pressure conditions, C 1-4 The gaseous component, naphtha-like C 5-12 In this thermal decomposition process under atmospheric pressure, light hydrocarbons and longer-chain hydrocarbons are vaporized and discharged to the top of the reactor, while residual wax that has not yet vaporized remains at the bottom of the reactor. However, the discharge from the top of the reactor contains a large amount of high-boiling-point components, resulting in a limited yield of high-value light hydrocarbon oil, and an excessive amount of heavy oil components and residual wax discharged.

[0027] Therefore, in order to increase the selectivity for conversion to light hydrocarbons during the thermal decomposition of waste plastics, the present invention adjusts the pressure of the reactor to a pressure higher than atmospheric pressure, for example, more than 1 bar to 40 bar, preferably 2 to 30 bar, and more preferably 5 to 10 bar, while the thermal decomposition of the molten waste plastic is being carried out. More specifically, a pressure control valve (PCV) is provided at the top of the reactor, and if gas above a certain pressure is generated while the thermal decomposition reaction of waste plastics is being carried out, the internal pressure of the reactor is adjusted to a pressure higher than atmospheric pressure by exhausting using the valve, thereby continuously discharging the gas generated during the thermal decomposition reaction to the top of the reactor.

[0028] By adjusting the high pressure of such a pyrolysis reactor, the vaporization of high-boiling-point components during the pyrolysis reaction can be suppressed, and the liquid residence time of these high-boiling-point components in the reactor can be increased. This increase in liquid residence time improves the efficiency of the decomposition reaction of waste plastics and increases the selectivity for conversion to light hydrocarbons, thereby enabling the production of high-value-added light hydrocarbon oil in high yield.

[0029] In other words, if the pressure of the pyrolysis reactor is adjusted to be higher than atmospheric pressure, the pyrolysis reaction of waste plastics may take place for 1 to 8 hours, more specifically 2 to 6 hours, due to the increased liquid residence time, and in this process, light hydrocarbons are converted from polymers, for example, C 5-12 This can increase the proportion of hydrocarbons that are converted to hydrocarbons.

[0030] In contrast, when the pyrolysis reaction is carried out at atmospheric pressure or lower, the vaporization of high-boiling-point components cannot be efficiently suppressed, and the proportion of high-boiling-point components with more than 12 carbon atoms in the upper discharge stream of the reactor may increase. When the pyrolysis reaction is carried out at a pressure exceeding 40 bar, C 5-12 The hydrocarbons cannot be discharged to the top of the reactor and can remain inside the reactor for a long time. Therefore, non-condensable pyrolysis byproduct gases that cannot be liquefied at room temperature (e.g., C 1-4 Excess gas may be produced.

[0031] On the one hand, considering that the waste plastic raw material is mainly a thermoplastic resin, for example, a mixture containing polyethylene with a number average molecular weight of 10,000 to 500,000, specifically 100,000 to 300,000 based on the number average molecular weight, or polypropylene with a number average molecular weight of 5,000 to 300,000, specifically 10,000 to 200,000, it is advantageous that the pyrolysis reaction is carried out in the range of 400 to 450 °C, specifically 420 to 430 °C. When the pyrolysis temperature is less than 400 °C, the pyrolysis rate may become slow. When it exceeds 450 °C, the pyrolysis rate is fast, but excessive solid carbides such as char may be generated due to high heat.

[0032] By the pyrolysis reaction, 20 to 90% by weight or 25 to 80% by weight of the weight of the waste plastic raw material can be generated as pyrolysis gas and discharged to the upper part of the reactor.

[0033] Specifically, the upper discharge stream of the reactor may be a gas-phase stream containing hydrocarbons of C 1-4 hydrocarbons, light hydrocarbons of C 5-12 intermediate hydrocarbons of C 13-22 and heavy hydrocarbons of C 23-40 Among these, hydrocarbons of C 1-4 such as methane, ethane, and propane are evaporated and separated due to non-condensability, and the remaining hydrocarbons can be condensed and obtained as liquid distillation oil.

[0034] The condensation process involves cooling the pyrolysis gas, thereby suppressing the polymerization reaction of hydrocarbons in the high-temperature pyrolysis gas discharged from the pyrolysis reactor and reducing the heat load on subsequent processes (purification processes). For example, by supplying the gas phase stream discharged from the top of the pyrolysis reactor to a condenser and performing heat exchange with quench oil or quench water, cooling and condensation occur to obtain liquid oil, which is then discharged to the bottom of the condenser and transferred to a storage tank. The cooling temperature due to the heat exchange may be 0 to 50°C, more specifically 20 to 30°C. On the other hand, gas components that are not condensed by the heat exchange (e.g., C 1-4 The gas is discharged upwards and, after subsequent processes such as compression, can be used as a heat source in petrochemical processes.

[0035] After the aforementioned thermal decomposition, the liquid oil that has been transferred to the storage tank after condensation is C 5-12 Light oil (LO), C 13-22 Middle oil (MO), and C 23-40 It may also contain heavy oil (HO), of which C 5-12 The content of diesel fuel (LO) may be 30 to 100% by weight, more specifically 35 to 99% by weight, based on the total weight of the liquid oil. Also, C 5-12 The diesel fuel (LO) content may be 20-70% by weight, more specifically 25-50% by weight, based on the weight of the waste plastic raw material before thermal decomposition.

[0036] In other words, the present invention suppresses the vaporization of high-boiling-point components by performing thermal decomposition of waste plastics under pressure conditions higher than atmospheric pressure, thereby improving the selectivity of light hydrocarbons in the thermal decomposition products. 5-12 This allows for the production of diesel fuel (LO) in high yield.

[0037] On the other hand, in the thermal decomposition reaction, some of the molten waste plastic cannot be vaporized and remains at the bottom of the reactor in the form of liquid oil. A reduced pressure treatment and condensation are performed to induce the further vaporization of this residual oil (S2).

[0038] The aforementioned depressurization treatment may be carried out in a flash method, where the pressure is reduced to atmospheric pressure (1 bar) after the previous pyrolysis reaction. This promotes the vaporization of components that did not vaporize in the previous pyrolysis step and remained at the bottom of the reactor, thereby increasing the yield of liquid oil and minimizing the amount of residual wax discharged. In this case, if the heat treatment is carried out under high pressure conditions, as in the previous pyrolysis, it is difficult to induce sufficient vaporization of the residual oil.

[0039] During such reduced-pressure treatment, the reactor may be heated to perform heat treatment simultaneously. The heat treatment may be carried out in a temperature range of 400 to 450°C, and additional thermal decomposition of residual oil may occur during this process. In this case, if the heat treatment temperature is below 400°C, it is difficult to induce sufficient vaporization of the residual oil, and if it exceeds 450°C, the formation of solid carbides such as char may be accelerated.

[0040] Furthermore, the vacuum treatment may be appropriately determined considering the composition of the residual oil remaining at the bottom of the reactor, and may be performed for, for example, 1 to 8 hours, or more specifically, 2 to 6 hours. If necessary, the reduced pressure and heat treatment may be carried out using another screw-type or plug-flow type reactor.

[0041] The gas produced by the aforementioned vacuum treatment can be obtained as liquid oil through condensation. The condensation may be carried out in the same manner as during thermal decomposition. The liquid oil obtained by the heat treatment may also be collected in a storage tank before being transferred to the subsequent refining step.

[0042] Subsequently, the liquid oil obtained in the pyrolysis and reduced-pressure treatment steps is purified for component separation (S3). The liquid oil obtained in the previous step is a mixed oil containing light and longer-chain hydrocarbons, and is therefore fed into a multi-stage distillation column for a refining process in which it is separated in stages based on the difference in boiling points.

[0043] The refining process may be carried out in a manner common in the field and is not particularly limited. For example, the feedstream supplied to the distillation column may contain all light and heavy oil components obtained by the thermal decomposition of waste plastics, and a stream containing low-boiling-point light hydrocarbons may be discharged from the upper part of the distillation column, while a stream containing high-boiling-point heavy hydrocarbons may be discharged from the lower part of the distillation column.

[0044] The feedstream supplied to the distillation column consists of the oil component obtained by the thermal decomposition of waste plastics, i.e., C 5-12 Diesel fuel (LO), C 13-22 Medium Oil (MO), and C 23-40 It may also be a mixed oil containing heavy oil (HO), and C is placed at the top of the distillation column. 5-12 The stream containing the light components can be separated and discharged.

[0045] In one embodiment of the present invention, C is separated at the top of the distillation column. 5-12 The light hydrocarbons may be present in the feedstream, i.e., 30-99% by weight, more specifically 35-99% by weight, of the total weight of the liquid oil (mixed oil). C obtained in such high yield 5-12 These light hydrocarbons, after condensation, can be usefully used as high-grade fuel oils.

[0046] In particular, the C obtained in the present invention 5-12 This light hydrocarbon fuel oil has a boiling point of 0 to 230°C, specifically 30 to 216°C, a kinematic viscosity at 40°C of 0.3 to 1.0 cSt, specifically 0.4 to 0.9 cSt, and a flash point of -80°C or higher (e.g., -40°C), making it useful as a petrochemical raw material.

[0047] According to the present invention as described above, the thermal decomposition of waste plastics can be performed under high-pressure conditions higher than atmospheric pressure to suppress the vaporization of high-boiling-point components and selectively increase the residence time of liquid components in the reactor, thereby improving the decomposition efficiency of waste plastics. This makes it possible to increase the selectivity and productivity of light hydrocarbon oils in the thermal decomposition products.

[0048] Furthermore, after thermal decomposition under the aforementioned high-pressure conditions, the oil remaining in the reactor can be subjected to a reduced pressure treatment at a lower pressure (for example, atmospheric pressure of 1 bar) to increase the vaporization of liquid hydrocarbons, thereby increasing the yield of the thermally decomposed oil and minimizing the discharge of residual wax.

[0049] Furthermore, utilizing light hydrocarbon oil obtained from the thermal decomposition of waste plastics can reduce greenhouse gas emissions caused during the supply of raw materials in petrochemical processes, improve process efficiency such as saving energy consumption, and is also environmentally advantageous because no harmful gases are generated during the processing of waste plastics.

[0050] The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only, and it will be obvious to an ordinary person that various changes and modifications are possible within the scope and technical concept of the present invention, and the scope of the present invention is not limited to these examples alone.

[0051] Example 1: As shown in Figure 1, 100 parts by weight of molten waste plastic containing polyethylene (PE) and polypropylene (PP) in a weight ratio of 6:4 was supplied to a stirred tank reactor. After heating the reactor using an external heating means, when the temperature reached 430°C, the thermal decomposition reaction was carried out for 2 hours while maintaining a constant temperature. During this time, the internal pressure of the reactor was adjusted to 2 bar by using a pressure regulating valve located at the top of the reactor to discharge the gas generated during the thermal decomposition reaction.

[0052] The gas generated during the thermal decomposition reaction was continuously discharged to the top of the reactor, flowed into a condenser connected to the reactor, and cooled to 25°C to obtain condensed liquid oil, after which the uncondensed gaseous components were discharged.

[0053] Next, the oil remaining at the bottom of the reactor was transferred to a subsequent screw-type reactor arranged in series, where it was heat-treated at 450°C while being reduced to atmospheric pressure (1 bar), and then condensed to obtain additional liquid oil. The liquid oil obtained above is supplied to a distillation column and purified by separating it according to its boiling point, C 5-12 This ultimately produced light hydrocarbon pyrolysis oil.

[0054] Example 2: The same procedure as in Example 1 was followed, except that the internal pressure of the reactor where the thermal decomposition was carried out was adjusted to 5 bar.

[0055] Example 3: The same procedure as in Example 1 was followed, except that the internal pressure of the reactor where the thermal decomposition was carried out was adjusted to 10 bar.

[0056] Example 4: The same procedure as in Example 1 was followed, except that the internal pressure of the reactor where the thermal decomposition was carried out was adjusted to 20 bar.

[0057] Example 5: The same procedure as in Example 1 was followed, except that the internal pressure of the reactor where the thermal decomposition was carried out was adjusted to 30 bar.

[0058] Comparative Example 1: The same procedure as in Example 1 was followed, except that the internal pressure of the reactor where the thermal decomposition takes place was adjusted to atmospheric pressure.

[0059] Figures 1-6 show the compositions of the pyrolysis products of Examples 1-5 and Comparative Example 1, respectively. Specifically, the compositions were determined by using the region-specific peak area ratios based on the number of carbon atoms in the mass spectrometry spectra obtained by GC-MS analysis, and by the non-condensable C 1-4 Gas, condensed liquid distilled oil (C 5-12 Diesel fuel (LO), C 13-22 Medium Oil (MO), and C 23-40 The fraction of heavy fuel oil (HO), and residual oil was calculated. Table 1 below shows the LO(C) in liquid oil under thermal decomposition conditions. 5-12 ) fraction and LO(C) relative to the amount of waste plastic raw material supplied 5-12 The yield was shown.

[0060] [Table 1] JPEG0007910280000002.jpg150130JPEG0007910280000003.jpg135131

[0061] From Table 1 above, Examples 1 to 5, in which the thermal decomposition of waste plastics was carried out under high-pressure conditions of 2 to 30 bar, showed a higher LO(C) content in the liquid oil compared to Comparative Example 1, in which thermal decomposition was carried out at atmospheric pressure. 5-12 ) fraction and LO(C) relative to the amount of waste plastic raw material supplied 5-12 It can be confirmed that the yield of ) has improved. This result is due to the fact that thermal decomposition carried out by adjusting the internal pressure of the reactor to be higher than atmospheric pressure suppresses the vaporization of high-boiling-point components, thereby increasing the residence time of the liquid components in the reactor and improving the efficiency of decomposition of waste plastics.

[0062] More specifically, Examples 1-3 show that by thermal decomposition at a pressure of 2-10 bar, C is extracted from waste plastic raw materials. 5-12 In Examples 4 and 5, by adjusting the pressure to the relatively high pressures of 20 bar and 30 bar, the light hydrocarbons did not completely vaporize and remained as residual oil. However, by lowering the pressure during additional pyrolysis and vaporizing the light hydrocarbons from the residual oil through the flash effect, the overall yield of light hydrocarbon pyrolysis oil relative to the raw material supply amount was improved.

[0063] On the other hand, in Comparative Example 1, thermal decomposition under atmospheric pressure at 430°C increased the content of vaporized components in the decomposition reaction of the waste plastic molten material, but the selectivity of higher light hydrocarbons in the resulting liquid oil decreased.

Claims

1. (S1) A step of supplying waste plastic raw material to a pyrolysis reactor and performing pyrolysis, and after discharging the gas phase stream generated by the pyrolysis to the top, condensing it to obtain liquid oil, (S2) The oil remaining at the bottom of the pyrolysis reactor is subjected to reduced pressure treatment and condensation to obtain liquid oil, (S3) A step of refining the liquid oil obtained in steps (S1) and (S2), Includes, The thermal decomposition in step (S1) is carried out by adjusting the internal pressure of the reactor to a range of over 1 bar to 40 bar. During the reduced pressure treatment in step (S2), the reactor is heated to perform additional heat treatment. A method for producing waste plastic pyrolysis oil, wherein the vacuum treatment of the residual oil is performed at a pressure of 1 bar and a temperature range of 400 to 450°C.

2. The method for producing waste plastic pyrolysis oil according to claim 1, wherein the pyrolysis in step (S1) is carried out by adjusting the internal pressure of the reactor to a range of 2 to 30 bar.

3. The method for producing waste plastic pyrolysis oil according to claim 1, wherein the pyrolysis in step (S1) is carried out at 400 to 450°C.

4. The liquid oil obtained in step (S1) is C ５－１２ Diesel fuel (light oil, LO), C １３－２２ Medium oil (MO), and C ２３－４０ A method for producing waste plastic pyrolysis oil according to claim 1, wherein the mixed oil contains heavy oil (HO).

5. Said C ５－１２ The method for producing waste plastic pyrolysis oil according to claim 4, wherein the content of light oil (LO) is 30 to 100% by weight based on the total weight of the liquid oil.

6. Said C ５－１２ The method for producing waste plastic pyrolysis oil according to claim 4, wherein the content of light oil (LO) is 20 to 70% by weight based on the weight of the waste plastic raw material.

7. The method for producing waste plastic pyrolysis oil according to claim 1, wherein the pyrolysis reactor is a reactor equipped with a stirrer.

8. A method for producing waste plastic pyrolysis oil according to any one of claims 1 to 7, wherein the waste plastic raw material is a mixture containing polyethylene (PE) or polypropylene (PP).

9. A method for producing waste plastic pyrolysis oil according to any one of claims 1 to 7, wherein the waste plastic raw material is supplied to a pyrolysis reactor after undergoing a pretreatment process including crushing, washing, drying, and melting.

Images