Method of preparing pyrolysis fuel oil from waste plastics

Abstract

The present invention relates to a method of preparing pyrolysis fuel oil from waste plastics, the method comprising the steps of: (A) preparing a waste plastic raw material; (B) supplying the waste plastic raw material to the lower part of a reaction distillation column and then pyrolyzing to generate pyrolysis gas; (C) supplying a hydrogen donor stream to the upper part of the reaction distillation column and reacting with the pyrolysis gas; and (D) discharging the pyrolysis gas that has reacted with the hydrogen donor stream to the upper part and condensing to obtain liquid oil.

Description

Method for producing pyrolysis oil from waste plastic

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0117692, filed September 5, 2023, and Korean Patent Application No. 10-2024-0091880, filed July 11, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a method for producing pyrolysis oil from waste plastic, and more specifically, to a method for producing high-quality light hydrocarbon oil with reduced olefin content in waste plastic pyrolysis oil.

[0005] Recently, the development and use of plastics with properties required for various applications and purposes is increasing. Plastics consume significant energy from crude oil extraction to manufacturing, and the process emits significant carbon emissions. Furthermore, when plastics used in various products are discarded, environmental pollution and enormous disposal costs occur, making recycling of waste plastics a critical social issue.

[0006] Generally, recycling methods for waste plastic (resin) include mechanical recycling, chemical recycling, and thermal recycling. Mechanical recycling involves crushing and sorting collected waste plastic, separating it by type, melting it using an extruder, and pelletizing it. This process involves mixing it with virgin plastic at a specific ratio or reinforcing it with functional additives to create resin products. Chemical recycling utilizes various chemical means to extract specific polymers or recover pure single molecules for repolymerization. Thermal recycling involves incinerating waste plastic to recover heat energy.

[0007] In particular, the above chemical recycling can reduce greenhouse gases compared to incineration of waste plastics and has recently been attracting attention in terms of developing alternative fuels.

[0008] Specifically, for chemical recycling of waste plastics, melted waste plastics (WP) made of materials such as polyethylene or polypropylene are fed to a reactor, pyrolyzed at a specific temperature, and the pyrolysis products are fed to a separation tower and separated according to boiling point, and then a purification process is performed to produce C such as naphtha. 5-12 Light oil (LO), long-chain heavy oil (HO), and high-boiling-point residual oil (RO) can be obtained. However, light oil such as naphtha obtained through this process has a problem of high olefin content. The olefin contained in the naphtha promotes the production of tar when fed into the naphtha cracking center (NCC) process, which causes coking. Therefore, if the olefin content in naphtha is high, it can lower the product yield and quality when fed into the NCC.

[0009] Accordingly, a method of converting olefins into paraffins using hydrogen gas has been proposed to reduce the olefin content, but hydrogen gas is expensive and equipment for recycling unreacted hydrogen gas is also expensive, making it economically difficult to apply to actual processes.

[0010] Therefore, a technology for reducing the olefin content in the production of light hydrocarbon oils such as naphtha is required.

[0011] The problem to be solved in the present invention is to reduce the olefin content from the pyrolysis oil of waste plastic to produce high-quality, high-value-added light oil in order to solve the problem mentioned in the background technology of the above invention.

[0012] However, the problems that the present invention seeks to solve are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0013] According to one embodiment of the present invention for solving the above problem, a method for producing pyrolysis oil from waste plastic is provided, comprising the steps of: preparing a waste plastic raw material; supplying the waste plastic raw material to the lower part of a reaction distillation column and then pyrolyzing it to generate pyrolysis gas; supplying a hydrogen donor stream to the upper part of the reaction distillation column and reacting it with the pyrolysis gas; and discharging the pyrolysis gas reacted with the hydrogen donor stream to the upper part and then condensing it to obtain a liquid oil.

[0014] According to the method for producing pyrolysis oil from waste plastic of the present invention, high-quality light hydrocarbon oil can be obtained by reducing the olefin content in the pyrolysis oil using an inexpensive hydrogen donor compound without using expensive hydrogen (H2) gas.

[0015] In addition, by lowering the olefin content in pyrolysis oil, tar production can be prevented from being promoted when light hydrocarbon oil is introduced into the NCC process.

[0016] Furthermore, by using a reaction distillation column, the thermal decomposition process of waste plastic and the purification process of separating thermal decomposition oil in stages by boiling point difference can be performed in a single device, and the economic feasibility can be improved by making it easy to recycle unreacted hydrogen donating compounds.

[0017] The effects that can be obtained from this invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art to which the present invention pertains from the description below.

[0018] Figure 1 is a flow chart of a process for manufacturing pyrolysis oil from waste plastic according to one embodiment.

[0019] Figure 2 is a flow chart of a process for manufacturing pyrolysis oil from waste plastic according to one embodiment.

[0020] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0021] In connection with the description of the drawings, similar reference numerals may be used for similar or related components.

[0022] The singular form of a noun corresponding to an item may include one or more of said items, unless the relevant context clearly indicates otherwise.

[0023] In this disclosure, each of the phrases "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 of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0024] The term “and / or” includes any combination of a plurality of related described elements or any one of a plurality of related described elements.

[0025] Terms such as "first," "second," or "first" or "second" may be used simply to distinguish one component from another and do not qualify the components in any other respect (e.g., importance or order).

[0026] In addition, terms such as 'front', 'rear', 'top', 'bottom', 'side', 'left', 'right', 'upper', and 'lower' used in this application are defined based on the drawings, and the shape and position of each component are not limited by these terms.

[0027] The terms “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the present disclosure, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0028] When a component is said to be “connected,” “coupled,” “supported,” or “in contact with” another component, this includes not only cases where the components are directly connected, coupled, supported, or in contact, but also cases where the components are indirectly connected, coupled, supported, or in contact through a third component.

[0029] When we say that a component is “on” another component, this includes not only cases where the component is in contact with the other component, but also cases where there is another component between the two components.

[0030] In addition, the terms "about", "substantially", etc. used herein are used in the sense of or close to the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly using the disclosure contents in which exact or absolute numerical values ​​are mentioned to aid understanding of the present invention.

[0031] The term "stream" as used herein may refer to the flow of fluid within a process, or may refer to the fluid itself flowing within a pipe. Specifically, the stream may refer to both the fluid itself flowing within the pipe connecting each device and the flow of the fluid. Furthermore, the fluid may include one or more components of gas, liquid, and solid.

[0032] The term “C” used herein n " represents all hydrocarbons with n carbon atoms. For example, "C 5-12 ” represents all hydrocarbon molecules with 5 to 12 carbon atoms, and “C 13-22 " represents all hydrocarbon molecules with 13 to 22 carbon atoms, and "C 23-40 " represents all hydrocarbon molecules having 23 to 40 carbon atoms.

[0033] The term “liquid oil” as used herein means the product obtained by converting the gaseous stream obtained in the pyrolysis step into a liquid phase by condensation, and may also be referred to as “liquid distilled oil”.

[0034] “Pressure” as referred to herein means gauge pressure measured relative to atmospheric pressure.

[0035] The “boiling point” referred to herein means the boiling point at atmospheric pressure (1 bar).

[0036] The pyrolysis gas referred to herein means gaseous pyrolysis oil.

[0037] A method for producing pyrolysis oil from waste plastic according to one embodiment of the present invention comprises: (A) a step of preparing a waste plastic raw material, (B) a step of pyrolysis of the waste plastic raw material, (C) a step of removing olefins using a hydrogen donating compound, and (D) a step of obtaining liquid oil by condensation.

[0038] Hereinafter, a method for producing pyrolysis oil from waste plastic according to the present invention will be described in detail step by step with reference to the drawings.

[0039] Figures 1 and 2 are flow charts of a process for manufacturing pyrolysis oil from waste plastic according to one embodiment.

[0040] First, prepare the waste plastic raw material (1) (A).

[0041] The above waste plastic raw material (1) may include a natural polymer, a synthetic polymer, or a mixture thereof, and the synthetic polymer may include a thermoplastic resin such as polyethylene (PE), polypropylene (PP), polystyrene, etc. In addition, the thermoplastic resin may be mixed with another type of resin such as polyvinyl chloride (PVC), polyethylene terephthalate (PET), or a thermosetting resin.

[0042] After being collected and sorted, the waste plastic raw material (1) of this type may undergo a pretreatment process including crushing, washing, drying, and melting. The pretreatment process may be performed in a manner conventional in the art.

[0043] For example, the size of the shredding of waste plastic is not particularly limited, but can typically be performed in the range of about 0.5 cm to 6.0 cm. Afterwards, the shredded waste plastic that has been washed and dried can be melted by putting it into an incinerator (100) as shown in Fig. 2 or a tubular melter such as an extruder. The extruder has a function of melting and kneading and then extruding, and can be, for example, a twin-screw extruder.

[0044] When the above waste plastic raw material (1) is a thermoplastic resin, for example, polyethylene, polypropylene, or a mixture thereof, the melting temperature may be about 120°C to 400°C, preferably about 320°C to 380°C, but is not limited thereto. The higher the melting temperature, the lower the viscosity of the molten waste plastic, which has the advantage of enabling fluid transport using a pump.

[0045] Meanwhile, referring to FIG. 2, the waste plastic melt may be heated by a heating means (110) provided outside the reaction distillation tower (200) before being supplied to the reaction distillation tower (200) described later. The heating means (110) may be positioned at the front end of the reaction distillation tower (200) and may be 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 heat transfer fluid through a jacket, but there is no particular limitation thereto. For example, the waste plastic melt may be heated to a temperature of about 400°C to 450°C, specifically, about 420°C to 430°C, through the heating means (110) for the pyrolysis reaction in the reaction distillation tower (200) described later. Meanwhile, a reboiler (not shown) may be additionally installed outside the reaction distillation tower (200) for the purpose of maintaining the temperature of the reaction distillation tower (200).

[0046] Next, the waste plastic melt obtained through the above pretreatment process is supplied as a raw material to the lower part of the reaction distillation tower (200) and then thermally decomposed to generate thermal decomposition gas (B).

[0047] The above reactive distillation column (200) is a multi-stage distillation column equipped with a plurality of trays (not shown), and performs a pyrolysis reaction (B) of waste plastic raw material (1) in a sump region at the bottom of the reactive distillation column (200) to generate a pyrolysis gas, and can perform a purification process of separating the pyrolysis gas into gas and liquid in stages based on the boiling point difference. The number of stages and the size of the reactive distillation column are not particularly limited, and can be set based on the theoretical number of stages inferred from a distillation curve considering the composition of the waste plastic raw material. Here, the "theoretical number of stages" means the number of virtual regions or stages in which two phases, such as gas and liquid phases, are in equilibrium with each other in the reactive distillation column. For example, the reactive distillation column (200) may have a multi-stage structure of 20 to 50 stages. As the temperature gradually decreases toward the upper stage of the reaction distillation tower, hydrocarbon components with relatively high boiling points can be separated from the lower stage, and carbon-hydrogen components with relatively low boiling points can be separated from the upper stage.

[0048] Referring to FIGS. 1 and 2, waste plastic raw material (1) is supplied to a sump at the bottom of a reaction distillation column (200), and a pyrolysis reaction (B) of the waste plastic raw material (1) is performed in the sump to generate pyrolysis gas. Here, the sump may refer to an area at the bottom of the reaction distillation column (200) below the lowest tray where a liquid raw material is received. In addition, the waste plastic raw material (1) may be supplied below the liquid level of the waste plastic raw material received in the sump of the reaction distillation column.

[0049] In a typical waste plastic pyrolysis process, waste plastic raw materials are pyrolyzed in a reactor and then naphtha (naphtha) is separated from the pyrolysis oil in a distillation device. On the other hand, in the present invention, by using a reactive distillation column (200), the equipment for the pyrolysis and separation process of waste plastic can be integrated to configure an efficient process. In addition, since the temperature at which the hydrogen-donating compound, which will be described later, reacts with the pyrolysis gas is approximately 200°C to 350°C, a separate temperature control facility is required to react the pyrolysis gas and the hydrogen-donating compound in the existing method. On the other hand, when using a reactive distillation column (200) as in the present invention, the hydrogen-donating compound can be introduced into a stage exhibiting the above temperature range without a separate facility to react the pyrolysis gas and the hydrogen-donating compound. Furthermore, when using a typical reactor, since the pyrolysis reaction continues during the residence time of the waste plastic in the reactor, the naphtha produced before the reactor residence time elapses may be over-cracked, which may reduce the final naphtha yield. On the other hand, in the case of using a reaction distillation tower (200) as in the present invention, the naphtha that is first thermally decomposed in the sump where the thermal decomposition reaction is in progress is directly discharged without additional thermal decomposition and moves to the upper distillation separation stage, so that the occurrence of an over-decomposition reaction can be suppressed, and thus there is an advantage of improving the naphtha yield.

[0050] In one embodiment of the present invention, the thermal decomposition reaction of the waste plastic melt may be performed at a temperature of about 400°C to 450°C, specifically, about 420°C to 430°C, but is not limited thereto. The waste plastic may be a mixture containing a thermoplastic resin, for example, 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 about 10,000 to 500,000 and / or polypropylene having a number average molecular weight of about 5,000 to 300,000, but is not limited thereto. Considering that the waste plastic is a thermoplastic resin, when the thermal decomposition temperature is 400°C or lower, the thermal decomposition rate may be slow, and when it exceeds 450°C, the thermal decomposition rate may be fast, but due to the high heat, an excessive amount of solid carbide such as char may be generated.

[0051] In addition, considering the naphtha yield, the operating pressure inside the reaction distillation tower (200) for the thermal cracking reaction can be adjusted to a range of about 1 to 20 bar, specifically about 1 to 5 bar. Satisfying the operating pressure can minimize excessive thermal cracking of naphtha or failure to convert to naphtha during thermal cracking.

[0052] In one embodiment of the present invention, as a pyrolysis product obtained by pyrolyzing the waste plastic melt, non-condensable C 1-4 Components such as naphtha, which can be converted into liquid oil by condensation 5-12 It may include pyrolysis gas containing light components and longer-chain heavy hydrocarbon components, and high-boiling residues that are not completely decomposed and thus not vaporized.

[0053] In addition, the low molecular weight components produced by the pyrolysis may include saturated and unsaturated hydrocarbons. Here, the low molecular weight component may refer to a light hydrocarbon having 12 or fewer carbon atoms, and more specifically, the saturated hydrocarbon of the low molecular weight component may include naphtha, and the unsaturated hydrocarbon of the low molecular weight component may refer to an olefin having 12 or fewer carbon atoms. For example, the low molecular weight component may include about 60 to 90 vol% of a light saturated hydrocarbon and about 10 to 40 vol% of a light unsaturated hydrocarbon based on the total volume of the low molecular weight component produced by the pyrolysis, and preferably, may include about 80 to 90 vol% of a light saturated hydrocarbon and about 10 to 20 vol% of a light unsaturated hydrocarbon, but is not limited thereto.

[0054] Through the above pyrolysis reaction (B), 20 wt% to 90 wt% or 25 wt% to 80 wt% of the total weight of the waste plastic raw material can be generated as pyrolysis gas and moved to the upper part of the reaction distillation tower (200), and the high boiling point residue that is not vaporized remains at the lower part of the reaction distillation tower (200). Specifically, the product pyrolyzed in the above pyrolysis step (B) is C 5-12 About 10 wt% to 60 wt% of light hydrocarbons, C 13-40 30 to 50 wt% of heavy hydrocarbons and C 40 It may contain from 10 to 50 wt% of excess high boiling point residue.

[0055] More specifically, the pyrolysis gas is C 1-4 Hydrocarbons of C 5-12 Light hydrocarbons, C 13-22 Intermediate hydrocarbons and C 23-40 It may be a gaseous stream containing heavy hydrocarbons. Among these, C such as methane, ethane, and propane 1-4The hydrocarbons are separated by evaporation due to their non-condensability, and the remaining hydrocarbons can be condensed and obtained as liquid distillate oil. Meanwhile, the high boiling point residue that was not vaporized can be discharged as the bottom discharge stream (4) of the reaction distillation tower (200).

[0056] Meanwhile, a process of separating and purifying a portion of the pyrolysis gas at an arbitrary stage within the reaction distillation tower (200) may be additionally included, as needed, before or after supplying the hydrogen donor stream (2) described later. Specifically, a hydrocarbon component having a boiling point of about 200°C or higher among the pyrolysis gas generated in the pyrolysis step (B) may be separated and purified.

[0057] In one embodiment of the present invention, as shown in FIG. 2, the method may further include a step of separating at least one hydrocarbon component among a hydrocarbon component (7) having a boiling point of 350°C to 570°C and a hydrocarbon component (8) having a boiling point of 200°C to less than 350°C among the pyrolysis gas generated in the pyrolysis step (B).

[0058] More specifically, the hydrocarbon component (7) having a boiling point of 350°C to 570°C is C 23-40 It may include heavy oil (HO) of C, and the hydrocarbon component (8) having a boiling point of less than 200°C to 350°C is C 13-22 It may contain middle oil (MO).

[0059] In detail, in order to separate the hydrocarbon component (7) having a boiling point of 350°C to 570°C among the pyrolysis gas, C is supplied in front of the hydrogen donating stream (2) to be described later. 23-40By performing a separation process on heavy oil of the above, a carbon-hydrogen component having a relatively high boiling point can be obtained, but is not limited thereto. In addition, in order to separate the hydrocarbon component (8) having a boiling point of 200°C to 350°C among the pyrolysis gas, C is supplied after the hydrogen donor stream (2) to be described later. 13-22 A hydrocarbon component having a relatively low boiling point can be obtained by performing a separation process on the intermediate oil and discharging it, but is not limited thereto.

[0060] For example, referring to FIG. 2, in the case of separating both the hydrocarbon component (8) having a boiling point of 200°C to 350°C and the hydrocarbon component (7) having a boiling point of 350°C to 570°C among the pyrolysis gas, the pyrolysis gas generated at the bottom of the reaction distillation tower (200) moves upward and first separates the hydrocarbon component (7) having a relatively high boiling point, thereby generating C 23-40 Obtain heavy oil (HO) of C and then separate the hydrocarbon component (8) having a relatively low boiling point. 13-22 Middle oil (MO) can be obtained. In addition, the remaining pyrolysis gas after the separation process moves to the top of the reaction distillation tower (200) as a gaseous stream containing hydrocarbon components having a boiling point of less than about 200°C.

[0061] Meanwhile, referring to FIG. 2, the high-boiling-point residue that is not vaporized among the thermal decomposition products can be discharged to the bottom discharge stream (5) of the reaction distillation column using a liquid pump (400) due to its high viscosity. The high-boiling-point residue has low utility because it hinders process operation or causes a decline in the quality of the final product.

[0062] More specifically, the bottom discharge stream (5) of the reaction distillation tower (200) is fractionated and discharged as a liquid stream containing a high-boiling-point residue (6), and the remaining liquid stream can be recycled back to the reaction distillation tower (200). Meanwhile, the high-boiling-point residue (6) at the bottom of the reaction distillation tower may be discharged in the form of a high-viscosity wax. Here, the recycling of the bottom discharge stream of the reaction distillation tower (200) can be performed to secure a sufficient flow rate to prevent fouling in the pipe due to char. Furthermore, the bottom discharge stream (5) can be connected to a reboiler (not shown) additionally provided outside the reaction distillation tower to maintain the fluid temperature at the bottom of the reaction distillation tower (200) while reducing char production, but is not limited thereto.

[0063] Next, a hydrogen donor stream (2) is supplied to the upper part of the reaction distillation tower (200) to react with the pyrolysis gas (C).

[0064] In one embodiment of the present invention, the hydrogen donating stream (2) comprises a hydrogen donating compound. The hydrogen donating compound is a donating compound that provides hydrogen to an olefin, which is an unsaturated hydrocarbon, and functions to convert the olefin in the pyrolysis gas into paraffin by replacing the double bond with hydrogen, and comprises at least one compound other than hydrogen (H2). Specifically, the hydrogen donating compound may include at least one functional group 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 200°C. For example, the hydrogen donating compound may include at least one compound selected from low molecular weight alcohols having 1 to 8 carbon atoms, ethylene glycol, and formic acid.

[0065] Among the pyrolysis oils produced during the pyrolysis of waste plastics, the fraction vaporized into light hydrocarbons (e.g., naphtha) with a boiling point of 50°C to less than 200°C contains a large amount of olefins. If pyrolysis oils with a high olefin content are used in the NCC process, there is a problem of causing tar production. Therefore, in the present invention, as illustrated in FIG. 1, a hydrogen donor stream (2) is supplied to an arbitrary stage at the top of a reaction distillation column (200) to react the olefins contained in the pyrolysis gas with a hydrogen donor compound (H-donor), and through the reaction, the double bonds of the olefins, which are unsaturated hydrocarbons, are replaced with hydrogen to convert them into paraffins, thereby reducing the olefin content in the pyrolysis gas. At this time, the paraffin produced through the hydrogen substitution reaction may be discharged together with a hydrocarbon component (8) having a boiling point of 200°C to less than 350°C, or may be discharged together with a hydrocarbon component (4) having a boiling point of 50°C to less than 200°C, but is not limited thereto.

[0066] According to one embodiment of the present invention, the hydrogen donor stream (2) may be supplied to a stage of 15% to 60% of the theoretical plate number from the top of the reaction distillation column (200), preferably 15% to 50%, and more preferably 15% to 40%. For example, when the number of theoretical plates of the reaction distillation column is 100, the uppermost stage may be stage 1, the lowest stage may be stage 100, and stages of 50% or less of the number of theoretical plates may refer to stages 1 to 50 of the reaction distillation column. By supplying the hydrogen donor stream (2) to a stage of the reaction distillation column (200) within the above range, the condition for excellent reactivity between olefin and hydrogen donor compound (H-donor) can be satisfied, and thus the olefin removal rate can be improved.

[0067] More specifically, in the hydrogen donor stream supply step (C), the hydrogen donor stream (2) may be introduced into a stage that is operated in a temperature range of 200°C to 400°C, preferably in a temperature range of 200°C to 380°C, and more preferably in a temperature range of 250°C to 350°C. If the operating temperature of the stage into which the hydrogen donor stream (2) is introduced is too low, the reaction between the olefin in the pyrolysis gas and the hydrogen donor compound (H-donor) may not occur, thereby lowering the olefin removal performance. On the other hand, the higher the operating temperature, the better the reactivity between the olefin in the pyrolysis gas and the hydrogen donor compound (H-donor). However, if the operating temperature of the stage into which the hydrogen donor stream is introduced is too high, the hydrogen substitution reaction between the pyrolysis gas and the hydrogen donor compound may be lowered, which may cause a problem.

[0068] As described above, when pyrolysis oil, including naphtha, is used as a feed for the NCC process, there is a problem that the olefin concentration is high, which causes tar formation. In the past, a method of converting olefins into paraffins using hydrogen (H2) was considered, but when using hydrogen (H2) gas, the cost of hydrogen and the price of a condenser for recycling the hydrogen (H2) gas are high, which reduces economic feasibility. In the present invention, in order to solve the problems of the prior art, a hydrogen donor compound, which is an inexpensive hydrogen source (H-source), can be used, thereby eliminating the use of expensive hydrogen (H2) gas. In addition, a general liquid pump can be used when recycling the hydrogen donor compound, so there is an advantage in that the process can be configured and operated economically.

[0069] In the above hydrogen donating stream supply step (C), the hydrogen donating 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, based on the total weight of the waste plastic raw material (1), but is not limited thereto. If the amount of the hydrogen donating stream (2) introduced is too small, the amount of hydrogen to be donated to olefin in the pyrolysis gas may be insufficient, resulting in a deterioration in olefin removal performance. If the amount of the hydrogen donating stream (2) introduced is too large, oxides may be generated by the hydrogen donating compound, resulting in a problem of not reaching the naphtha cracker specification.

[0070] In one embodiment of the present invention, as shown in FIG. 2, when hydrocarbon components having a boiling point of 200°C or higher are first separated and recovered, the pyrolysis gas may contain a high proportion of hydrocarbon components having a boiling point of less than 200°C when the hydrogen donor stream (2) is supplied.

[0071] Meanwhile, when supplying the hydrogen donating stream (2), a reaction catalyst may be further added to increase the rate of olefin removal in the pyrolysis gas. Specifically, as illustrated in FIG. 2, a catalyst layer (210) for supplying the reaction catalyst may be provided above the position where the hydrogen donating 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 donating stream (2) and the olefin in the pyrolysis gas, and may include, for example, one or more metal components selected from the group consisting of nickel (Ni), silicon (Si), and aluminum (Al), but is not limited thereto. More specifically, a catalyst in the form of Ni supported on a Si / Al support may be used as the metal-based catalyst, wherein the support can promote pyrolysis and the support can promote the hydrogen donating reaction.

[0072] More specifically, the amount of the reaction catalyst to be introduced 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 donating stream (2), but is not limited thereto. By introducing the reaction catalyst, the olefin removal effect may be improved, but if the amount of the reaction catalyst introduced is excessive, an overreaction problem may occur.

[0073] Afterwards, the pyrolysis gas reacted with the hydrogen donating stream is discharged as an upper discharge stream (3) and then condensed to obtain liquid oil (4) (D).

[0074] The upper discharge stream (3) of the above reaction distillation tower (200) may be a gaseous stream containing light hydrocarbon components having a boiling point of less than 200°C and unreacted hydrogen donating compounds, and more specifically, non-condensable C 1-4 Components such as naphtha, which can be converted into liquid oil by condensation 5-12 It may include light components and unreacted hydrogen donating compounds. Furthermore, the light components having 12 or fewer carbon atoms may include saturated hydrocarbon components such as naphtha and unsaturated hydrocarbon components such as olefins.

[0075] After the upper discharge stream (3) of the reaction distillation tower (200) is discharged, it can be obtained as liquid oil (4) through a condensation process. The condensation is a process of cooling the pyrolysis gas, thereby suppressing the polymerization reaction of hydrocarbons in the high-temperature pyrolysis gas discharged from the reaction distillation tower (200) and reducing the heat load of the subsequent process.

[0076] Referring to FIG. 1, the pyrolysis gas reacted with the hydrogen donating stream is discharged to the upper part of the reaction distillation tower (200) as an upper discharge stream (3) and supplied to a condenser (300) and heat exchanged with quench oil or quench water is performed, so that cooling and condensation occur to obtain a liquid oil (4), and finally, the liquid oil (4) is obtained by phase separation from the unreacted hydrogen donating compound in the condenser (300). The cooling temperature due to the heat exchange may be about 0°C to 50°C, specifically about 20°C to 30°C.

[0077] Specifically, the liquid oil obtained in the condensation step (D) has a boiling point of C of 50°C to less than 200°C. 5-12 It may include light oil (LO). More specifically, the liquid oil obtained in the condensation step (D) contains C, a saturated hydrocarbon component, based on the total weight. 5-12 It may contain 10 to 60 wt% of hard oil, specifically 30 to 50 wt%.

[0078] Meanwhile, the liquid oil obtained in the condensation step (D) may contain olefin, which is an unsaturated hydrocarbon component, 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 Light saturated hydrocarbon oil (naphtha) can be obtained, and tar formation occurring when inputting into the NCC process can be minimized. Furthermore, the liquid oil obtained in the condensation step (D) may further include a residual amount of unreacted hydrogen donating compounds.

[0079] In one embodiment of the present invention, the upper discharge stream (3) of the reaction distillation tower transferred to the condenser (300) is composed of unreacted hydrogen donating compounds, which are polar components, and C, which is a non-polar component. 5-12 It may contain a hard component of. Accordingly, in the condensation step (D), the condensed unreacted hydrogen donating compound has a different polarity of C 5-12 The light saturated hydrocarbon oil can be separated from the layer and discharged as the first lower discharge stream (9) of the condenser (300).

[0080] Referring to FIG. 2, the first bottom discharge stream (9) of the condenser (300) containing the unreacted hydrogen donating compound can be recycled to the hydrogen donating stream (2) of the hydrogen donating stream supply step (C). More specifically, the unreacted hydrogen donating compound in the reaction distillation column (200) has a low boiling point and is discharged as a gaseous top discharge stream (3) together with the pyrolysis gas, and is introduced into the condenser (300) and condensed, and in the condenser (300), the unreacted hydrogen donating compound, which is a polar component, is converted into the non-polar component C. 5-12 The light saturated hydrocarbon oil is separated from the layer and discharged as the first bottom discharge stream (9) of the condenser (300) and can be reused as the hydrogen donor stream (2) of the reaction distillation tower (200). The first bottom discharge stream (9) of the condenser (300) is a liquid stream, and thus the unreacted hydrogen donor compound can be easily transported at low cost using a liquid pump or the like, so there is an advantage of economic reuse.

[0081] Additionally, the second bottom discharge stream of the condenser (300) containing naphtha can be refluxed to the top of the reaction distillation tower (200). The second bottom discharge stream is a stream recycled to increase the naphtha purity of the top discharge stream (3) separated and discharged to the top of the reaction distillation tower (200), and a minimum amount that satisfies the target naphtha purity can be refluxed to the top of the reaction distillation tower (200).

[0082] Meanwhile, in the condensation step (D), the uncondensed gas stream (10) can be recycled as the process gas of the raw material preparation step (A). Specifically, the gas component that is not condensed in the heat exchange of the condenser (300), for example, C 1-4 The hydrocarbon gas of the condenser (300) can be discharged as the upper discharge stream (10) and used as process gas. Referring to FIG. 2, the upper discharge stream (10) of the condenser (300) can be used as incinerator fuel (100) of the 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 incinerator (100) fuel without using additional external energy, energy usage can be reduced and process efficiency can be increased.

[0083] Above, the method for producing pyrolysis oil from waste plastic according to the present invention has been described with reference to the drawings, but this describes and illustrates only the core components for understanding the present invention, and in addition to the processes and devices described and illustrated in the drawings, processes and devices not described or illustrated separately can be appropriately applied and utilized to carry out the method for producing pyrolysis oil from waste plastic according to the present invention.

[0084] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present invention, and the scope of the present invention is not limited to these examples alone.

[0085] [Example]

[0086] Comparative Example 1

[0087] 300 parts by weight of waste plastic melt containing polyethylene (PE) and polypropylene (PP) in a weight ratio of 6:4 was placed in a reactor and heated to 430°C to perform a pyrolysis reaction, thereby obtaining pyrolysis oil.

[0088] Example 1

[0089] As shown in Fig. 1, 300 parts by weight of waste plastic melt containing polyethylene (PE) and polypropylene (PP) in a weight ratio of 6:4 was heated to 430°C with a heater and then supplied to a reaction distillation tower (200) to perform a thermal decomposition reaction. Subsequently, 100 parts by weight of formic acid was supplied from the top of the reaction distillation tower (200) to a stage corresponding to 15% of the theoretical number of plates and reacted at 200°C. That is, the flow rate ratio of the waste plastic melt and formic acid in Example 1 was 3:1.

[0090] Example 2

[0091] The same process as Example 1 was performed, except that 100 parts by weight of formic acid was added to 40% of the theoretical number of plates from the top of the reaction distillation tower (200) and the reaction was performed at 350°C. That is, the flow rate ratio of the waste plastic melt and formic acid in Example 2 was 3:1.

[0092] Example 3

[0093] The same process as Example 1 was performed, except that 150 parts by weight of methanol (MeOH) was added to 40% of the theoretical number of plates from the top of the reaction distillation tower (200) and the reaction was performed at 350°C. That is, in Example 3, the flow rate ratio of the waste plastic melt and methanol was 2:1.

[0094] Example 4

[0095] The same process as Example 1 was performed, except that 150 parts by weight of methanol (MeOH) and 2.25 parts by weight of Ni / SiAl catalyst were added to 40% of the theoretical number of plates from the top of the reaction distillation tower (200) and the reaction was performed 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.

[0096] Example 5

[0097] The same process as Example 1 was performed, except that 150 parts by weight of methanol (MeOH) was added to 60% of the theoretical number of plates from the top of the reaction distillation tower (200) and the reaction was performed at 400°C. That is, in Example 3, the flow rate ratio of the waste plastic melt and methanol was 2:1.

[0098] Experimental Example: Comparison of Olefin Contents

[0099] In order to confirm the content of olefin contained in the pyrolysis oil finally obtained from waste plastic in Examples 1 to 5 and Comparative Example 1, the bromine number (BN) was measured according to the ASTM D1159 method, and the results are shown in Table 1 below.

[0100] Specifically, the bromine number (g / 100 g) is a numerical value indicating unsaturated bonds, and represents the amount (g) of bromine substituted for the double bonds of unsaturated components, i.e. olefins, in 100 g of a sample, and a lower bromine number means a lower olefin content.

[0101] Classification H-donor type Pyrolysis oil standard H-donor input theoretical plate number Reaction temperature (℃) Bromine number (BN) H-donor weight ratio Catalyst weight ratio Comparative example 1-----29.9 Example 1 Formic acid 1 / 3-15% 200 24.1 Example 2 Formic acid 1 / 3-40% 350 17.2 Example 3 Methanol 1 / 2-40% 350 21.8 Example 4 Methanol 1 / 2 0.0 0 75 40% 350 13.5 Example 5 Methanol 1 / 2-60% 400 25.4

[0102] Referring to Table 1 above, it can be confirmed that the bromine value of the pyrolysis oil of Examples 1 to 5 reacted with hydrogen-donating compounds such as formic acid or methanol was reduced compared to Comparative Example 1, which only performed a pyrolysis reaction on waste plastic. This confirms that the olefin content in the pyrolysis oil was reduced when reacted with a hydrogen-donating compound.

[0103] More specifically, Examples 1 and 2 and Examples 3 and 5 used the same amount and type of hydrogen donating compound, but only the reaction temperature was different.

[0104] Comparing Examples 1 and 2, the bromine number of Example 2, in which formic acid was supplied from the top of the reaction distillation column (200) to 15% of the theoretical number of plates and the pyrolysis oil and the hydrogen donating compound were reacted at 200°C, was measured to be lower than that of Example 1, in which formic acid was supplied from the top of the reaction distillation column (200) to 40% of the theoretical number of plates and the reaction was performed at a higher temperature of 350°C. This indicates that the higher the operating temperature at the position where the hydrogen donating compound is introduced in the reaction distillation column, the better the olefin removal effect can be.

[0105] However, comparing Examples 3 and 5, in Example 5, where methanol was supplied from the top of the reaction distillation tower (200) to 60% of the theoretical plates and the pyrolysis oil and the hydrogen donating compound were reacted at 400°C, a lower bromine number was measured compared to Example 3, where methanol was supplied from the top of the reaction distillation tower (200) to 40% of the theoretical plates and the reaction was performed at 350°C. This indicates that if the operating temperature at the location where the hydrogen donating compound is introduced in the reaction distillation tower becomes excessively high, the olefin removal effect may actually decrease.

[0106] Meanwhile, Example 4 is a case where only a reaction catalyst was added when a hydrogen donating compound was added in Example 3. Comparing Examples 3 and 4, the bromine number of Comparative Example 4 using a reaction catalyst was measured to be lower than that of Example 3 where a reaction catalyst was not used. 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 an olefin and a hydrogen donating compound.

[0107] Although exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and those skilled in the art will understand that various changes and modifications are possible within the scope and spirit of the claims set forth below.

[0108] [Explanation of symbols]

[0109] 1: Waste plastic raw material

[0110] 2: Hydrogen donor stream

[0111] 3: Top discharge stream of the reaction distillation column

[0112] 4: Hydrocarbon components having a boiling point of 50°C to less than 200°C

[0113] 5: Bottom discharge stream of the reaction distillation column

[0114] 6: High boiling point residue

[0115] 7: Hydrocarbon component having a boiling point of 350℃ to 570℃

[0116] 8: Hydrocarbon components having a boiling point of 200°C to less than 350°C

[0117] 9: First lower discharge stream of the condenser

[0118] 10: Top discharge stream of the condenser

[0119] 100: Incinerator, 110: Heating means

[0120] 200: Reaction distillation tower, 300: Condenser, 400: Pump

Claims

1. (A) Step for preparing waste plastic raw materials; (B) A step of supplying the above waste plastic raw material to the bottom of a reaction distillation tower and then thermally decomposing it to generate thermal decomposition gas; (C) a step of supplying a hydrogen donor stream to the upper part of the reaction distillation column to react with the pyrolysis gas; and (D) A method for producing pyrolysis oil from waste plastic, comprising the step of discharging the pyrolysis gas reacted with the hydrogen donating stream upward and then condensing it to obtain liquid oil.

2. In paragraph 1, A method for producing pyrolysis oil from waste plastic, wherein the hydrogen donating stream comprises at least one compound selected from low molecular alcohols having 1 to 8 carbon atoms, ethylene glycol, and formic acid.

3. In paragraph 1, A method for producing pyrolysis oil from waste plastic, comprising supplying the hydrogen donating stream to a unit operated in a temperature range of 200°C to 400°C in the above step (C).

4. In paragraph 1, A method for producing pyrolysis oil from waste plastic, comprising supplying the hydrogen donating stream at a flow rate ratio of 1:0.01 to 1:1 with respect to the total weight of the waste plastic raw material in the step (C).

5. In paragraph 1, A method for producing pyrolysis oil from waste plastic, comprising adding a reaction catalyst in the above step (C).

6. In paragraph 1, The liquid oil obtained in the above step (D) has a boiling point of 50°C to less than 200°C. 5-12 A method for producing waste plastic pyrolysis oil, including light oil (LO).

7. In paragraph 6, A method for producing waste plastic pyrolysis oil, comprising olefin in an amount of 25% by volume or less based on the total volume of liquid oil obtained in the above step (D).

8. In paragraph 1, Before the above step (C), it further includes a step of separating at least one hydrocarbon component among hydrocarbons having a boiling point of 200°C to 350°C and hydrocarbons having a boiling point of 350 to 570°C among the pyrolysis gas generated in the above step (B), The hydrocarbon having a boiling point of less than 200°C to 350°C is C 13-22 The hydrocarbons containing middle oil (MO) and having a boiling point of 350°C to 570°C are C 23-40 A method for producing pyrolysis oil from waste plastic, comprising heavy oil (HO).

9. In paragraph 1, A method for producing pyrolysis oil from waste plastic, further comprising, in step (D), separating the unreacted hydrogen donating compound from the liquid oil and recycling it into the hydrogen donating stream of step (C).

10. In paragraph 1, The above waste plastic raw material is a method for producing pyrolysis oil of waste plastic, which is a mixture containing polyethylene (PE) or polypropylene (PP).

11. In paragraph 1, A method for producing pyrolysis oil from waste plastic, wherein the operating pressure inside the above reaction distillation column is in the range of 1 bar to 20 bar.

12. In paragraph 1, A method for producing pyrolysis oil from waste plastic, wherein the reaction distillation tower has a multi-stage structure of 20 to 50 stages.

13. In paragraph 1, A method for producing pyrolysis oil from waste plastic, comprising discharging a bottom discharge stream containing residue from the bottom of the reaction distillation tower, and fractionating a portion of the bottom discharge stream and returning it to the reaction distillation tower.

14. In paragraph 1, The above step (A) includes a step of melting the waste plastic raw material, A method for producing pyrolysis oil from waste plastic, comprising using the uncondensed gas stream in the above step (D) as fuel for melting the waste plastic raw material.

15. In paragraph 1, A method for producing pyrolysis oil from waste plastic, wherein the hydrogen donating stream is supplied from the top of the reaction distillation tower to a stage of 15% to 60% of the theoretical number of stages.

Images