Method for producing waste plastic pyrolysis oil

Abstract

The present invention relates to a method for producing waste plastic pyrolysis oil, which includes the steps of: (A) preparing a waste plastic raw material; (B) supplying the waste plastic raw material to the lower part of a reactive distillation column and then pyrolyzing it to generate a pyrolysis gas; (C) supplying a hydrogen donor stream to the upper part of the reactive distillation column to react with the pyrolysis gas; and (D) discharging the pyrolysis gas that has reacted with the hydrogen donor stream to the upper part and then condensing it to obtain a liquid oil.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0117692 filed on September 5, 2023, and Korean Patent Application No. 10-2024-0091880 filed on July 11, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a method for producing waste plastic pyrolysis oil, and more particularly to a method for producing high-quality light hydrocarbon oil with a reduced olefin content from waste plastic pyrolysis oil. [Background technology]

[0003] In recent years, the development and use of plastics with properties suited to various uses and purposes has increased. Plastics require a lot of energy from crude oil extraction to manufacturing, and a large amount of carbon is emitted during the process. Furthermore, when plastics used in various products are discarded, environmental pollution and huge disposal costs occur, making waste plastic recycling an important 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 collected waste plastics, separating them by type, and then melting and pelletizing them using an extruder. The pellets are then mixed with new materials in a certain ratio or reinforced with functional additives to produce resin products. Chemical recycling involves using various chemical means to extract only specific polymers, or recovering them as pure monomolecules and repolymerizing them. Thermal recycling involves burning waste plastics and recovering the heat energy.

[0005] In particular, chemical recycling can reduce greenhouse gas emissions compared to incineration of waste plastics, and has been attracting attention in recent years from the perspective of developing alternative fuels.

[0006] Specifically, for chemical recycling of waste plastics, melted waste plastics (WP) such as polyethylene or polypropylene are fed to a reactor and pyrolyzed at a specific temperature. The pyrolysis products are then fed to a separation tower and separated according to their boiling points. This results in the production of C12, such as naphtha. 5-12 The resulting products are light oil (LO), longer-chain heavy oil (HO), and high-boiling residue (RO). However, the light oils, such as naphtha, obtained through this process have a problem of high olefin content. The olefins contained in the naphtha promote tar formation and cause coking when fed to the naphtha cracking center (NCC) process. Therefore, if the olefin content in naphtha is high, it can reduce the product yield and quality when fed to the NCC process.

[0007] Therefore, a method of converting olefins into paraffins using hydrogen gas has been proposed to reduce the olefin content. However, hydrogen gas is expensive, and the equipment for recycling unreacted hydrogen gas is also expensive, making this method economically difficult to apply to actual processes. Therefore, there is a need for a technology that can reduce the olefin content during the production of light hydrocarbon oils such as naphtha. Summary of the Invention [Problem to be solved by the invention]

[0008] The problem to be solved by the present invention is to reduce the olefin content from waste plastic pyrolysis oil and produce high-quality, high-value-added diesel fuel in order to solve the problems described in the background of the invention above.

[0009] However, the problems that the present application aims to solve are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0010] In order to solve the above problems, according to one embodiment of the present invention, there is provided a method for producing waste plastic pyrolysis oil, including the steps of preparing a waste plastic raw material, supplying the waste plastic raw material to a lower part of a reactive distillation column and pyrolyzing the waste plastic raw material to generate a pyrolysis gas, supplying a hydrogen donor stream to an upper part of the reactive distillation column to react with the pyrolysis gas, and discharging the pyrolysis gas that has reacted with the hydrogen donor stream to the upper part and condensing it to obtain a liquid oil. [Effects of the Invention]

[0011] According to the method for producing waste plastic pyrolysis oil of the present invention, high-quality light hydrocarbon oil can be obtained by reducing the olefin content in the pyrolysis oil using a low-cost hydrogen donor compound without using expensive hydrogen (H) gas. Furthermore, by reducing the olefin content in the thermal cracking oil, it is possible to prevent the promotion of tar formation when the light hydrocarbon oil is fed to the NCC process.

[0012] Furthermore, by using a reactive distillation column, the waste plastic pyrolysis process and the refining process, in which the pyrolysis oil is separated into stages based on differences in boiling points, can be carried out in a single device, making it easy to recycle unreacted hydrogen-donor compounds and improving economic efficiency.

[0013] The effects obtained by the present application are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a flowchart of a process for producing pyrolysis oil from waste plastic according to one embodiment. [Figure 2] 1 is a flowchart of a process for producing pyrolysis oil from waste plastic according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] The terms and words used in the description of the present invention and the claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their inventions. In connection with the description of the drawings, like reference numerals may be used for like or related components.

[0016] The singular form of a noun referring to an item may include one or more of said items unless the relevant context clearly dictates otherwise. In this disclosure, each of the phrases such as "A or B," "at least one of A and B," "at least one of A or B," "A, B, or C," "at least one of A, B, and C," and "at least one of A, B, or C" may include any one or all possible combinations of the items listed along with the corresponding phrase.

[0017] The term "and / or" includes a combination of two or more associated listed elements or any element of two or more associated listed elements.

[0018] Terms such as "first," "second," "first," or "second" may be used simply to distinguish the component from other components and do not limit the component in other respects (e.g., importance or order).

[0019] Furthermore, terms such as "front," "rear," "top," "bottom," "side," "left side," "right side," "upper," and "lower" used in this application are defined based on the drawings, and these terms do not limit the shape and position of each component.

[0020] Terms such as "comprise" or "have" specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof set forth in this disclosure, but do not preclude the possible presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0021] When a component is "connected," "coupled," "supported," or "in contact with" another component, this includes not only when the components are directly connected, coupled, supported, or in contact, but also when the components are indirectly connected, coupled, supported, or in contact via a third component.

[0022] A component being "located on" another component does not only mean that the component is in contact with the other component, but also means that there is another component between the two components.

[0023] Furthermore, when the terms "about," "substantially," and the like are used in this application, and when inherent manufacturing and material tolerances are given, the terms "about," "substantially," and the like are used to mean a numerical value or a value close to that numerical value, and are used to prevent unscrupulous infringers from unfairly utilizing the disclosure in which precise or absolute numerical values ​​are mentioned to aid in the understanding of the present invention.

[0024] The term "stream" as used herein refers to the flow of fluid during a process, and may also refer to the fluid itself flowing in a pipe. Specifically, the term "stream" may refer simultaneously to the fluid itself flowing in a pipe connecting each device and the flow of the fluid. The fluid may also contain one or more components of gas, liquid, and solid.

[0025] As used herein, the term "C n " refers to all hydrocarbons having n carbon atoms. For example, "C 5-12 " indicates all hydrocarbon molecules with 5 to 12 carbon atoms, and "C 13-22 " indicates all hydrocarbon molecules with carbon numbers between 13 and 22, and "C 23-40 " refers to all hydrocarbon molecules with 23 to 40 carbon atoms.

[0026] The term "liquid oil" as used herein means the product obtained by condensing the vapor stream obtained in the thermal cracking step into a liquid form, and may also be referred to as "liquid distilled oil."

[0027] "Pressure" as referred to in this application means gauge pressure measured relative to atmospheric pressure. The "boiling point" referred to in this application means the boiling point at normal pressure (1 bar). Pyrolysis gas as referred to in this application means pyrolysis oil in the gas phase.

[0028] A method for producing waste plastic pyrolysis oil according to one embodiment of the present invention includes (A) a step of preparing waste plastic raw material, (B) a step of thermally decomposing the waste plastic raw material, (C) a step of removing olefins using a hydrogen donor compound, and (D) a step of obtaining liquid oil by condensation.

[0029] Hereinafter, the method for producing waste plastic pyrolysis oil according to the present invention will be described in detail step by step with reference to the drawings. 1 and 2 are flowcharts showing a process for producing pyrolysis oil from waste plastic according to one embodiment.

[0030] First, a waste plastic raw material 1 is prepared (A). The waste plastic raw material 1 may include natural polymers, synthetic polymers, or a mixture thereof, and the synthetic polymers may include thermoplastic resins such as polyethylene (PE), polypropylene (PP), polystyrene, etc. The thermoplastic resin may also be mixed with other types of resins such as PVC (Polyvinyl chloride) and PET (Polyethylene terephthalate), or thermosetting resins.

[0031] After being collected and sorted, the waste plastic raw materials 1 of such materials may be subjected to a pre-treatment process including crushing, washing, drying, and melting, which may be carried out in a manner conventional in the art.

[0032] For example, the size of the crushed waste plastic is not particularly limited, but may generally be in the range of about 0.5 cm to 6.0 cm. After that, the crushed waste plastic that has been washed and dried may be fed into an incinerator 100 as shown in Fig. 2 or a tubular melting machine such as an extruder to be melted. The extruder has the function of melting, kneading, and extruding, and may be, for example, a twin-screw extruder.

[0033] When the waste plastic raw material 1 is a thermoplastic resin, such as polyethylene, polypropylene, or a mixture thereof, the melting temperature may be, but is not limited to, about 120° C. to 400° C., preferably about 320° C. to 380° C. The higher the melting temperature, the lower the viscosity of the molten waste plastic, which has the advantage of allowing the fluid to be transported using a pump.

[0034] Referring to FIG. 2, the waste plastic melt may be heated via a heating means 110 installed outside the reactive distillation column 200 before being supplied to the reactive distillation column 200 (described later). The heating means 110 may be located upstream of the reactive distillation column 200 and used as a heat source for the waste plastic pyrolysis reaction. For example, the heating means 110 may be an electric heater that transfers high-temperature heat to the waste plastic by passing high-temperature / high-pressure steam, hot water, or a heat transfer fluid through a jacket, but is not particularly limited thereto. For example, the waste plastic melt may be heated via the heating means 110 to a temperature of approximately 400°C to 450°C, specifically approximately 420°C to 430°C, for the pyrolysis reaction in the reactive distillation column 200 (described later). A reboiler (not shown) may be further installed outside the reactive distillation column 200 to maintain the temperature of the reactive distillation column 200.

[0035] Next, the molten waste plastic obtained through the pretreatment process is fed as a raw material to the lower part of the reactive distillation column 200 and then thermally decomposed to generate pyrolysis gas (B). The reactive distillation column 200 is a multi-stage distillation column equipped with multiple trays (not shown). A pyrolysis reaction (B) of waste plastic feedstock 1 is carried out in a sump region at the bottom of the reactive distillation column 200 to generate pyrolysis gas. The pyrolysis gas can then be purified by separating it into gas and liquid in stages based on the difference in boiling points. The number and size of the reactive distillation column are not particularly limited and can be determined based on the theoretical number of stages estimated from a distillation curve that takes into account the composition of the waste plastic feedstock. Here, the term "theoretical number of stages" refers to the number of imaginary regions or stages in the reactive distillation column where two phases, such as a gas phase and a liquid phase, are in equilibrium with each other. For example, the reactive distillation column 200 may have a multi-stage structure with 20 to 50 stages. The temperature gradually decreases as the stages in the reactive distillation column increase. Lower stages can separate relatively high-boiling hydrocarbon components, while upper stages can separate relatively low-boiling hydrocarbon components.

[0036] 1 and 2, waste plastic raw material 1 is supplied to a sump at the bottom of reactive distillation column 200, where a thermal decomposition reaction (B) of the waste plastic raw material 1 occurs, generating a pyrolysis gas. Here, the sump may refer to an area in the bottom of reactive distillation column 200 below the lowest tray where a liquid raw material is stored. In addition, waste plastic raw material 1 may be supplied from below the liquid surface of the waste plastic raw material stored in the sump of the reactive distillation column.

[0037] In a typical waste plastic pyrolysis process, waste plastic raw materials are thermally decomposed in a reactor, followed by separation of naphtha from the pyrolysis oil in a distillation apparatus. In contrast, the present invention uses a reactive distillation column 200 to integrate the waste plastic pyrolysis and separation process equipment, resulting in an efficient process. Furthermore, because the temperature at which the hydrogen donor compound (described below) reacts with pyrolysis gas is approximately 200°C to less than 350°C, a separate temperature control device is required to react the pyrolysis gas with the hydrogen donor compound in the conventional method. In contrast, when using a reactive distillation column 200 as in the present invention, the hydrogen donor compound can be introduced into a stage exhibiting the above temperature range without the need for separate equipment, allowing the pyrolysis gas and the hydrogen donor compound to react. Furthermore, when using a conventional reactor, the pyrolysis reaction continues during the waste plastic's residence time in the reactor, and naphtha produced before the reactor residence time has elapsed may be over-cracked, resulting in a reduced final naphtha yield. In contrast, when using the reactive distillation column 200 as in the present invention, naphtha that has been thermally cracked first in the sump where the thermal cracking reaction is progressing immediately leaves without additional thermal cracking and moves to the upper distillation separation stage. This has the advantage of suppressing the occurrence of over-cracking reactions and improving naphtha yield.

[0038] In one embodiment of the present invention, the thermal decomposition reaction of the molten waste plastic may be carried out at a temperature of approximately 400°C to 450°C, specifically, approximately 420°C to 430°C, but is not limited thereto. The waste plastic may be a thermoplastic resin, such as polyethylene, polypropylene, or a mixture thereof. For example, the waste plastic may be a mixture containing polyethylene having a number average molecular weight (Mn) of approximately 10,000 to 500,000 and / or polypropylene having a number average molecular weight of approximately 5,000 to 300,000, but is not limited thereto. Considering that the waste plastic is a thermoplastic resin, if the thermal decomposition temperature is 400°C or less, the thermal decomposition rate may be slow. If the thermal decomposition temperature is above 450°C, the thermal decomposition rate may be fast, but the high heat may result in the excessive production of solid carbonized materials such as char.

[0039] In addition, in consideration of naphtha yield, the operating pressure inside the reactive distillation column 200 for the thermal cracking reaction may be adjusted to a range of about 1 to 20 bar, specifically about 1 to 5 bar. By satisfying this operating pressure, excessive thermal cracking of naphtha or failure to convert naphtha into naphtha during thermal cracking can be minimized.

[0040] In one embodiment of the present invention, the pyrolysis product obtained by the pyrolysis reaction of the molten waste plastic includes uncondensed C 1-4 Components, such as naphtha, which can be converted into liquid oil by condensation 5-12 The pyrolysis gas may contain light components such as pyrolysis olefins, and heavier hydrocarbon components with longer chains, as well as high-boiling residues that were not completely cracked and vaporized.

[0041] The low molecular weight components produced by the thermal cracking may include saturated and unsaturated hydrocarbons. Here, the low molecular weight components refer to light hydrocarbons having 12 or less carbon atoms. More specifically, the saturated hydrocarbons of the low molecular weight components may include naphtha, and the unsaturated hydrocarbons of the low molecular weight components may refer to olefins having 12 or less carbon atoms. For example, the low molecular weight components may contain about 60% to 90% by volume of light saturated hydrocarbons and about 10% to 40% by volume of light unsaturated hydrocarbons relative to the total volume of the low molecular weight components produced by the thermal cracking, and preferably, may contain about 80% to 90% by volume of light saturated hydrocarbons and about 10% to 20% by volume of light unsaturated hydrocarbons, but are not limited thereto.

[0042] Through the pyrolysis reaction (B), 20 wt% to 90 wt% or 25 wt% to 80 wt% of the total weight of the waste plastic raw material is generated as pyrolysis gas, which can move to the upper part of the reactive distillation column 200, and the high boiling point residue that has not been vaporized remains in the lower part of the reactive distillation column 200. Specifically, the product pyrolyzed in the pyrolysis step (B) is C 5-12 About 10% by weight to 60% by weight of light hydrocarbons, C 13-40 30% by weight to 50% by weight of heavy hydrocarbons, and C 40 It may contain 10% to 50% by weight of excess high boiling residue.

[0043] More specifically, the pyrolysis gas is C 1-4 hydrocarbons, C 5-12 Light hydrocarbons, C 13-22 intermediate hydrocarbons, and C 23-40 The gaseous stream may contain heavy hydrocarbons such as methane, ethane, and propane. 1-4 The hydrocarbons in the reaction mixture are evaporated and separated due to their non-condensable nature, and the remaining hydrocarbons are condensed to obtain a liquid distillate oil, while the high-boiling residue that was not vaporized can be discharged as the bottom discharge stream 5 of the reactive distillation column 200.

[0044] Meanwhile, before or after the supply of the hydrogen donor stream 2 described below, a step of separating and purifying a part of the pyrolysis gas at any stage in the reactive distillation column 200 may be further included, as necessary. Specifically, hydrocarbon components having a boiling point of about 200°C or higher can be separated and purified from the pyrolysis gas generated in the pyrolysis step (B).

[0045] In one embodiment of the present invention, as shown in FIG. 2, the method may further include a step of separating one or more hydrocarbon components from the pyrolysis gas generated in the pyrolysis step (B), the hydrocarbon component 7 having a boiling point of 350°C to 570°C and the hydrocarbon component 8 having a boiling point of 200°C to less than 350°C.

[0046] More specifically, the hydrocarbon component 7 having a boiling point of 350°C to 570°C is C 23-40 The hydrocarbon component 8 having a boiling point of 200°C to less than 350°C may include heavy oil (HO). 13-22 It may also contain middle oil (MO).

[0047] In detail, in order to separate the hydrocarbon component 7 having a boiling point of 350°C to 570°C from the pyrolysis gas, a C 23-40 By subjecting the heavy oil to a separation process and discharging the resulting mixture, hydrocarbon components having relatively high boiling points can be obtained, but this is not limited to this. In addition, in order to separate the hydrocarbon components 8 having a boiling point of less than 200°C to 350°C from the pyrolysis gas, a C 200°C / C ... 13-22 By subjecting the middle oil to a separation process and discharging the oil, hydrocarbon components having relatively low boiling points can be obtained, but the present invention is not limited to this.

[0048] For example, referring to FIG. 2, when separating both the hydrocarbon component 8 having a boiling point of 200°C to less than 350°C and the hydrocarbon component 7 having a boiling point of 350°C to 570°C from the pyrolysis gas, the pyrolysis gas generated at the lower part of the reactive distillation column 200 moves to the upper part, and the hydrocarbon component 7 having a relatively high boiling point is first separated to form C 23-40 Heavy oil (HO) is obtained, and then hydrocarbon components 8 having relatively low boiling points are separated to obtain C 13-22 After the separation step, the residual pyrolysis gas moves to the top of the reactive distillation column 200 as a gaseous stream containing hydrocarbon components with a boiling point of less than about 200°C.

[0049] Meanwhile, referring to Figure 2, among the pyrolysis products, the high-boiling point residue that has not been vaporized can be discharged as bottom discharge stream 5 from the reactive distillation column using a liquid pump 400 due to its high viscosity. The high-boiling point residue is underutilized because it can hinder process operation or cause a decrease in the quality of the final product.

[0050] More specifically, the bottom discharge stream 5 from the reactive distillation column 200 is fractionated and discharged as a liquid phase stream containing a high-boiling point residue 6, and the remaining liquid phase stream can be recycled back to the reactive distillation column 200. Meanwhile, the high-boiling point residue 6 at the bottom of the reactive distillation column may be discharged as a highly viscous wax. The bottom discharge stream from the reactive distillation column 200 may be recycled to ensure a sufficient flow rate and prevent piping fouling due to char. Furthermore, the bottom discharge stream 5 may be connected to a reboiler (not shown) installed outside the reactive distillation column to maintain the fluid temperature at the bottom of the reactive distillation column 200 while reducing char production, but this is not limiting.

[0051] Next, a hydrogen donor stream 2 is supplied to the top of the reactive distillation column 200 to react with the pyrolysis gas (C). In one embodiment of the present invention, the hydrogen donor stream 2 includes a hydrogen donor compound. The hydrogen donor compound is a donating compound that provides hydrogen to olefins, which are unsaturated hydrocarbons, and serves to convert the olefins in the pyrolysis gas into paraffins by replacing the double bonds of the olefins with hydrogen. The hydrogen donor compound includes at least one compound other than hydrogen (H). Specifically, the hydrogen donor compound may include one or more functional groups selected from a hydroxyl group (-OH) and a carboxyl group (-COOH) and may be a compound having a boiling point of about 30°C to less than 200°C. For example, the hydrogen donor compound may include one or more compounds selected from low-molecular-weight alcohols having 1 to 8 carbon atoms, ethylene glycol, and formic acid.

[0052] Pyrolysis oil produced during the thermal decomposition of waste plastics contains a large amount of olefins, particularly in the fraction vaporized as light hydrocarbons (e.g., naphtha) with a boiling point of 50°C to less than 200°C. When pyrolysis oil with a high olefin content is used in the NCC process, there is a problem of tar formation. Therefore, as shown in FIG. 1, the present invention reduces the olefin content in the pyrolysis gas by supplying a hydrogen donor stream 2 to an arbitrary upper stage of a reactive distillation column 200 and reacting the olefins contained in the pyrolysis gas with a hydrogen donor compound (H-donor). The double bonds of the olefins, which are unsaturated hydrocarbons, are converted into paraffins by hydrogen substitution through the reaction, thereby reducing the olefin content in the pyrolysis gas. In this case, the paraffins produced by the hydrogen substitution reaction can be discharged together with hydrocarbon components 8 having a boiling point of 200°C to less than 350°C or hydrocarbon components 4 having a boiling point of 50°C to less than 200°C, but are not limited thereto.

[0053] According to one embodiment of the present invention, the hydrogen donor stream 2 may be supplied to 15% to 60%, preferably 15% to 50%, and more preferably 15% to 40% of the theoretical number of stages from the top of the reactive distillation column 200. For example, if the theoretical number of stages of the reactive distillation column is 100, the top stage may be stage 1 and the bottom stage may be stage 100. A stage that is 50% or less of the theoretical number of stages may refer to stages 1 to 50 of the reactive distillation column. Supplying the hydrogen donor stream 2 to the above-mentioned range of stages of the reactive distillation column 200 satisfies the requirement of excellent reactivity between olefins and the hydrogen donor compound (H-donor), thereby improving the olefin removal rate.

[0054] More specifically, in the hydrogen donor stream supply step (C), the hydrogen donor stream 2 may be fed to a stage operated at a temperature range of 200°C to 400°C, preferably 200°C to 380°C, and more preferably 250°C to 350°C. If the operating temperature of the stage to which the hydrogen donor stream 2 is fed is too low, the reaction between the olefins in the pyrolysis gas and the hydrogen donor compound (H-donor) may not occur, resulting in a decrease in olefin removal performance. On the other hand, the higher the operating temperature, the more the reactivity between the olefins in the pyrolysis gas and the hydrogen donor compound (H-donor). However, if the operating temperature of the stage to which the hydrogen donor stream is fed is too high, the hydrogen substitution reaction between the pyrolysis gas and the hydrogen donor compound may actually be reduced.

[0055] As mentioned above, when pyrolysis oil, including naphtha, is used as a feed for the NCC process, it generally has a high olefin concentration, which can lead to the formation of tar. Previously, methods of converting olefins to paraffins using hydrogen (H2) have been investigated, but the use of hydrogen (H2) gas results in high hydrogen costs and condensers for recycling the hydrogen (H2) gas, resulting in poor economic viability. The present invention solves these problems of the prior art by using a hydrogen-donor compound, which is a low-cost hydrogen source, thereby eliminating the need for expensive hydrogen (H2) gas. Furthermore, the present invention has the advantage of being able to use a conventional liquid pump when recycling the hydrogen-donor compound, thereby enabling the process to be configured and operated economically.

[0056] In the hydrogen donor stream supplying step (C), the hydrogen donor stream 2 may be introduced at a flow rate ratio of 1:0.01 to 1:1, preferably 1:0.3 to 1:0.5, relative to the total weight of the waste plastic feedstock 1, but is not limited thereto. If the amount of hydrogen donor stream 2 introduced is too small, the amount of hydrogen donated to the olefins in the pyrolysis gas may be insufficient, resulting in a decrease in olefin removal performance. If the amount of hydrogen donor stream 2 introduced is too large, the hydrogen donor compound may produce oxides, resulting in a problem of not meeting the naphtha cracker specifications.

[0057] In one embodiment of the present invention, as shown in FIG. 2, if hydrocarbon components with a boiling point of 200° C. or higher are first separated and recovered, the pyrolysis gas may contain a high proportion of hydrocarbon components with a boiling point of less than 200° C. when hydrogen donor stream 2 is fed.

[0058] Meanwhile, when supplying the hydrogen donor stream 2, a reaction catalyst may be further added to increase the rate of olefin removal from the pyrolysis gas. Specifically, as shown in FIG. 2, a catalyst layer 210 for supplying a reaction catalyst may be provided above the position where the hydrogen donor stream 2 is supplied. More specifically, a metal-based catalyst may be used as the reaction catalyst for promoting the hydrogen substitution reaction of the hydrogen donor stream 2 and the olefins in the pyrolysis gas. For example, the catalyst may include, but is not limited to, one or more metal components selected from the group consisting of nickel (Ni), silicon (Si), and aluminum (Al). More specifically, a catalyst in the form of Ni supported on a Si / Al support may be used as the metal-based catalyst. Here, the support promotes pyrolysis, and the support promotes the hydrogen-donating reaction.

[0059] More specifically, the amount of the reaction catalyst may be about 3 parts by weight or less, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the hydrogen donor stream 2. Although the addition of the reaction catalyst can improve the olefin removal effect, an excessive amount of the reaction catalyst can cause over-reaction.

[0060] Thereafter, the pyrolysis gas that has reacted with the hydrogen donor stream is discharged as an overhead discharge stream 3 and then condensed to obtain a liquid oil 4 (D). The top effluent stream 3 of the reactive distillation column 200 may be a vapor phase stream containing light hydrocarbon components having a boiling point below 200°C and unreacted hydrogen donor compounds, more specifically, uncondensable C 1-4 Components, such as naphtha, which can be converted into liquid oil by condensation 5-12 and unreacted hydrogen donor compounds. Furthermore, the light components having 12 or less carbon atoms may include saturated hydrocarbon components such as naphtha and unsaturated hydrocarbon components such as olefins.

[0061] After being discharged, the top discharge stream 3 of the reactive distillation column 200 undergoes a condensation process and can be obtained as a liquid oil 4. The condensation is a process of cooling the pyrolysis gas, which suppresses the polymerization reaction of hydrocarbons in the high-temperature pyrolysis gas discharged from the reactive distillation column 200 and reduces the heat load of subsequent processes.

[0062] 1, the pyrolysis gas reacted with the hydrogen donor stream is discharged as top discharge stream 3 from the top of the reactive distillation column 200 and supplied to condenser 300, where it is cooled and condensed by heat exchange with quench oil or quench water to obtain liquid oil 4. Finally, the pyrolysis gas is phase-separated from the unreacted hydrogen donor compound in condenser 300 to obtain liquid oil 4. The cooling temperature by the heat exchange may be about 0°C to 50°C, specifically about 20°C to 30°C.

[0063] Specifically, the liquid oil obtained in the condensation step (D) is a C 2 O 3 having a boiling point of 50°C to less than 200°C. 5-12 More specifically, the liquid oil obtained in the condensation step (D) may contain saturated hydrocarbon components such as C 5-12 The diesel fuel may be contained in an amount of 10% by weight to 60% by weight, specifically 30% by weight to 50% by weight, based on the total weight.

[0064] On the other hand, the liquid oil obtained in the condensation step (D) may contain olefins, which are unsaturated hydrocarbon components, in an amount of 25% by volume or less, specifically 1% by volume to 20% by volume, and more specifically 10% by volume to 20% by volume, based on the total volume. The lower the olefin content in the liquid oil obtained in the condensation step (D), the higher the purity of C 5-12 A light saturated hydrocarbon oil (naphtha) can be obtained, and the formation of tar generated when the liquid oil is introduced into the NCC process can be minimized. Furthermore, the liquid oil obtained in the condensation step (D) may further contain a residual amount of unreacted hydrogen donor compound.

[0065] In one embodiment of the present invention, the reactive distillation column top effluent stream 3 transferred to the condenser 300 contains polar components, unreacted hydrogen donor compounds, and non-polar components, C 5-12 Therefore, in the condensation step (D), the condensed unreacted hydrogen donor compound may contain light components of C having different polarities. 5-12 and can be discharged as a first bottom discharge stream 9 of the condenser 300.

[0066] 2, the first bottom discharge stream 9 of the condenser 300 containing the unreacted hydrogen donor compound can be recycled as the hydrogen donor stream 2 of the hydrogen donor stream supplying step (C). More specifically, in the reactive distillation column 200, the unreacted hydrogen donor compound has a low boiling point and is discharged as the vapor-phase top discharge stream 3 together with the pyrolysis gas, and flows into the condenser 300 to be condensed. In the condenser 300, the unreacted hydrogen donor compound, which is a polar component, is converted into the non-polar component C 5-12 The first lower discharge stream 9 from the condenser 300 is separated into layers from the light saturated hydrocarbon oil, discharged as a first lower discharge stream 9 from the condenser 300, and can be recycled as the hydrogen donor stream 2 from the reactive distillation column 200. The first lower discharge stream 9 from the condenser 300 is a liquid phase stream, and the unreacted hydrogen donor compound can be easily transported at low cost using a liquid pump or the like, which has the advantage of being economically recyclable.

[0067] In addition, the second bottom discharge stream of the condenser 300 containing naphtha may be refluxed to the upper part of the reactive distillation column 200. The second bottom discharge stream is a stream that is recycled to increase the naphtha purity of the upper discharge stream 3 separated and discharged to the upper part of the reactive distillation column 200, and a minimum amount that satisfies the target naphtha purity may be refluxed to the upper part of the reactive distillation column 200.

[0068] Meanwhile, in the condensation step (D), the uncondensed gas phase stream can be recycled as the process gas of the raw material preparation step (A). Specifically, the gas components that were not condensed by the heat exchange in the condenser 300, such as C 1-4 The hydrocarbon gas is discharged as an upper discharge stream 10 from the condenser 300 and may be used as a process gas. Referring to Fig. 2, the upper discharge stream 10 from the condenser 300 may be used as an incinerator fuel for an incinerator 100 in a melting process, which is a pretreatment process of waste plastic raw materials. In this way, by recycling the process gas 10 and using it as fuel for the incinerator 100 without using additional external energy, it is possible to reduce energy consumption and improve process efficiency.

[0069] The method for producing waste plastic pyrolysis oil according to the present invention has been described above with reference to the drawings. However, this only describes and illustrates the core configuration for understanding the present invention. In addition to the processes and devices described above and shown in the drawings, processes and devices not described or illustrated separately can be appropriately applied and used to implement the method for producing waste plastic pyrolysis oil according to the present invention.

[0070] 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 apparent to those skilled in the art that various changes and modifications can be made within the scope and technical concept of the present invention, and the scope of the present invention is not limited to these examples.

[0071] [Example] Comparative Example 1 300 parts by weight of molten waste plastic containing polyethylene (PE) and polypropylene (PP) in a weight ratio of 6:4 was placed in a reactor and heated to 430°C to carry out a pyrolysis reaction, yielding pyrolysis oil.

[0072] Example 1 As shown in Figure 1, 300 parts by weight of molten waste plastic containing polyethylene (PE) and polypropylene (PP) in a weight ratio of 6:4 was heated to 430°C using a heater and then supplied to a reactive distillation column 200 to carry out a thermal decomposition reaction. Next, 100 parts by weight of formic acid was added to a stage corresponding to 15% of the theoretical number of stages from the top of the reactive distillation column 200 and reacted at 200°C. That is, the flow rate ratio of the molten waste plastic to formic acid in Example 1 was 3:1.

[0073] Example 2 The same process as in Example 1 was carried out, except that 100 parts by weight of formic acid was added to 40% of the theoretical number of plates from the top of the reactive distillation column 200 and reacted at 350°C. That is, in Example 2, the flow ratio of the waste plastic melt to formic acid was 3:1.

[0074] Example 3 The same process as in Example 1 was carried out, except that 150 parts by weight of methanol (MeOH) was added to a stage corresponding to 40% of the theoretical number of stages from the top of the reactive distillation column 200 and reacted at 350°C. That is, in Example 3, the flow rate ratio of the waste plastic melt to methanol was 2:1.

[0075] Example 4 The same process as in Example 1 was carried out, except that 150 parts by weight of methanol (MeOH) and 2.25 parts by weight of Ni / SiAl catalyst were introduced into the stage corresponding to 40% of the theoretical number of stages from the top of the reactive distillation column 200 and reacted at 350°C. That is, the flow rate ratio of the waste plastic melt, methanol, and catalyst in Example 4 was 2:1:0.015.

[0076] Example 5 The same process as in Example 1 was carried out, except that 150 parts by weight of methanol (MeOH) was added to 60% of the theoretical number of plates from the top of the reactive distillation column 200 and reacted at 400°C. That is, the flow rate ratio of the waste plastic melt to methanol in Example 5 was 2:1.

[0077] Experimental example: Comparison of olefin content In Examples 1 to 5 and Comparative Example 1, the bromine number (BN) was measured according to ASTM D1159 to confirm the content of olefins contained in the pyrolysis oil finally obtained from the waste plastics, and the results are shown in Table 1 below.

[0078] Specifically, the bromine number (g / 100g) is a numerical value indicating unsaturated bonds, and indicates the amount (g) of unsaturated components in 100g of a sample, i.e., the amount of bromine substituted for olefin double bonds. A lower bromine number means a lower olefin content.

[0079] [Table 1]

[0080] Referring to Table 1, it can be seen that the bromine number of the pyrolysis oils of Examples 1 to 5, which were reacted with hydrogen donor compounds such as formic acid and methanol, was reduced compared to Comparative Example 1, in which waste plastics were only subjected to a pyrolysis reaction. This confirms that the olefin content in the pyrolysis oil was reduced during the reaction with the hydrogen donor compound. More specifically, Examples 1 and 2 and Examples 3 and 5 used the same amount and type of hydrogen donor compound, but only the reaction temperature was different.

[0081] Comparing Examples 1 and 2, in Example 1, formic acid was supplied to 15% of the theoretical plate number from the top of the reactive distillation column 200 and the pyrolysis oil and the hydrogen donor compound were reacted at 200°C. In Example 2, formic acid was supplied to 40% of the theoretical plate number from the top of the reactive distillation column 200 and the reaction was carried out at a higher temperature of 350°C. The bromine number was measured to be lower than in Example 1. This indicates that the higher the operating temperature at the position where the hydrogen donor compound is introduced in the reactive distillation column, the better the olefin removal effect.

[0082] However, comparing Examples 3 and 5, in Example 5, in which methanol was supplied to 60% of the theoretical number of stages from the top of the reactive distillation column 200 and the pyrolysis oil and the hydrogen donor compound were reacted at 400°C, a lower bromine number was measured compared to Example 3, in which methanol was supplied to 40% of the theoretical number of stages from the top of the reactive distillation column 200 and the reaction was carried out at 350°C. This indicates that if the operating temperature at the position where the hydrogen donor compound is introduced in the reactive distillation column is excessively high, the olefin removal effect may actually be reduced.

[0083] On the other hand, Example 4 is a case where only a reaction catalyst was added when the hydrogen donor compound was added in Example 3. Comparing Examples 3 and 4, the bromine number of Comparative Example 4, which used a reaction catalyst, was measured to be lower than that of Example 3, which did not use a reaction catalyst. Therefore, it can be confirmed that the olefin removal performance is further improved when a reaction catalyst is added during the hydrogen substitution reaction of olefins and a hydrogen donor compound.

[0084] Although exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and a person having ordinary knowledge in the art will understand that various changes and modifications are possible within the scope of the concept and scope of the claims set forth below. [Explanation of symbols]

[0085] 1: Waste plastic raw materials 2: Hydrogen donor stream 3: Top discharge stream of reactive distillation column 4: Hydrocarbon components with a boiling point of 50℃ to less than 200℃ 5: Bottom discharge stream of reactive distillation column 6: High boiling point residue 7: Hydrocarbon components with a boiling point between 350℃ and 570℃ 8: Hydrocarbon components with a boiling point of 200℃ to less than 350℃ 9: Condenser first lower discharge stream 10: Condenser top discharge stream 100: Incinerator 110: Heating means 200: Reactive distillation column 300: Condenser 400: Pump

Claims

1. (A) preparing a waste plastic raw material; (B) supplying the waste plastic raw material to the lower part of the reactive distillation column and then thermally decomposing it to generate pyrolysis gas; (C) supplying a hydrogen donor stream to the top of the reactive distillation column to react with the pyrolysis gas; (D) discharging the pyrolysis gas reacted with the hydrogen donor stream to the top and then condensing it to obtain a liquid oil; A method for producing waste plastic pyrolysis oil, comprising:

2. 2. The method for producing waste plastic pyrolysis oil according to claim 1, wherein the hydrogen donor stream contains one or more compounds selected from the group consisting of low-molecular-weight alcohols having 1 to 8 carbon atoms, ethylene glycol, and formic acid.

3. 2. The method for producing waste plastic pyrolysis oil according to claim 1, wherein in step (C), the hydrogen donor stream is supplied to a number of stages operated in a temperature range of 200°C to 400°C.

4. 2. The method for producing waste plastic pyrolysis oil according to claim 1, further comprising supplying the hydrogen donor stream at a flow rate ratio of 1:0.01 to 1:1 relative to the total weight of the waste plastic feedstock in step (C).

5. The method for producing waste plastic pyrolysis oil according to claim 1, further comprising adding a reaction catalyst in step (C).

6. The liquid oil obtained in the step (D) is a C 1000-1000-200°C-based oil having a boiling point of 50°C to less than 200°C. ５－１２ 2. The method for producing waste plastic pyrolysis oil according to claim 1, wherein the waste plastic pyrolysis oil contains light oil (LO).

7. The method for producing waste plastic pyrolysis oil according to claim 6, wherein the liquid oil obtained in step (D) contains olefins in an amount of 25% by volume or less relative to the total volume of the liquid oil.

8. The method further comprises, before the step (C), a step of separating one or more hydrocarbon components from the pyrolysis gas generated in the step (B) among hydrocarbons having a boiling point of 200°C to less than 350°C and hydrocarbons having a boiling point of 350 to 570°C; The hydrocarbon having a boiling point of 200°C to less than 350°C is C １３－２２ The hydrocarbons having a boiling point of 350°C to 570°C include C ２３－４０ The method for producing waste plastic pyrolysis oil according to claim 1, wherein the waste plastic pyrolysis oil contains heavy oil (HO).

9. 2. The method for producing waste plastic pyrolysis oil according to claim 1, further comprising: in step (D), phase-separating the unreacted hydrogen donor compound from the liquid oil and recycling the phase-separated hydrogen donor compound as the hydrogen donor stream in step (C).

10. The method for producing waste plastic pyrolysis oil according to claim 1, wherein the waste plastic raw material is a mixture containing polyethylene (PE) or polypropylene (PP).

11. The method for producing waste plastic pyrolysis oil according to claim 1, wherein the operating pressure inside the reactive distillation column is in the range of 1 bar to 20 bar.

12. The method for producing waste plastic pyrolysis oil according to claim 1, wherein the reactive distillation column has a multi-stage structure of 20 to 50 stages.

13. 2. The method for producing waste plastic pyrolysis oil according to claim 1, comprising: discharging a bottom discharge stream containing residue from the bottom of the reactive distillation column; and fractionating a portion of the bottom discharge stream and refluxing it to the reactive distillation column.

14. The step (A) includes a step of melting the waste plastic raw material, The method for producing waste plastic pyrolysis oil according to claim 1, wherein the gas phase stream not condensed in step (D) is used as fuel for melting the waste plastic raw material.

15. The method for producing waste plastic pyrolysis oil according to any one of claims 1 to 14, wherein the hydrogen donor stream is supplied to a stage that is 15% to 60% of the theoretical number of stages from the top of the reactive distillation column.

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